U.S. patent application number 17/610150 was filed with the patent office on 2022-07-14 for frame transmission method and device using multiple random backoff operation in broadband wireless communication network.
The applicant listed for this patent is Hyundai Motor Company, Kia Corporation, Korea National University of Transportation Industry-Academic Cooperation Foundation. Invention is credited to Yong Su Gwak, Yong Ho Kim.
Application Number | 20220225406 17/610150 |
Document ID | / |
Family ID | 1000006286931 |
Filed Date | 2022-07-14 |
United States Patent
Application |
20220225406 |
Kind Code |
A1 |
Kim; Yong Ho ; et
al. |
July 14, 2022 |
FRAME TRANSMISSION METHOD AND DEVICE USING MULTIPLE RANDOM BACKOFF
OPERATION IN BROADBAND WIRELESS COMMUNICATION NETWORK
Abstract
An operating method of a communication node in a wireless
communication network includes: performing a first monitoring
operation on a first link and a second link during a preset period;
performing a first random backoff operation in the first link for a
first random backoff period, if the first link and the second link
are in an idle state according to the first monitoring operation;
performing, in the second link, a second random backoff operation
for a second random backoff period which is different from the
first random backoff period in length; and transmitting a frame at
a same point in time in the first link and the second link, if the
first link is in the idle state according to the first random
backoff operation, and if the state of the second link is an idle
state according to execution of the second random backoff
operation.
Inventors: |
Kim; Yong Ho; (Incheon,
KR) ; Gwak; Yong Su; (Seoul, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Hyundai Motor Company
Kia Corporation
Korea National University of Transportation Industry-Academic
Cooperation Foundation |
Seoul
Seoul
Chungju-Si, Chungcheongbuk-Do |
|
KR
KR
KR |
|
|
Family ID: |
1000006286931 |
Appl. No.: |
17/610150 |
Filed: |
May 8, 2020 |
PCT Filed: |
May 8, 2020 |
PCT NO: |
PCT/KR2020/006127 |
371 Date: |
November 9, 2021 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04W 72/0446 20130101;
H04W 74/0866 20130101; H04L 1/1621 20130101; H04W 74/085
20130101 |
International
Class: |
H04W 74/08 20060101
H04W074/08; H04W 72/04 20060101 H04W072/04; H04L 1/16 20060101
H04L001/16 |
Foreign Application Data
Date |
Code |
Application Number |
May 9, 2019 |
KR |
2019-0054559 |
Claims
1. An operation method of a communication node in a wireless
communication network, the operation method comprising: performing
a first random backoff operation on a first link during a first
period, and performing a second random backoff operation on a
second link during a second period; in response to determining that
the first random backoff operation is completed and the second
random backoff operation is not completed, performing a monitoring
operation on the first link while performing the second random
backoff operation; in response to determining that the first link
is in an idle state as a result of the monitoring operation, and
that the second random backoff operation is completed, transmitting
a first frame on the first link and a second frame on the second
link, respectively, from a first time point.
2. The operation method according to claim 1, wherein the first
period and the second period have different durations.
3. The operation method according to claim 2, wherein the first
period is determined based on an access category corresponding to
the first frame, and the second period is determined based on an
access category corresponding to the second frame.
4. The operation method according to claim 1, wherein each of the
first frame and the second frame is a physical layer protocol data
unit (PPDU).
5. The operation method according to claim 1, wherein padding
bit(s) are added to at least one of the first frame and the second
frame so that the first frame and the second frame have a same
duration.
6. The operation method according to claim 1, wherein the first
time point is a completion time point of the second random backoff
operation, and the transmission of the first frame and the
transmission of the second frame are started simultaneously at the
first time point.
7. The operation method according to claim 1, wherein the
communication node is a non-simultaneous transmit and receive
(non-STR) multi-link device (MLD), and the communication node uses
different medium access control (MAC) layer addresses for the first
link and the second link.
8. An operation method of a communication node in a wireless
communication network, the operation method comprising: performing
a first random backoff operation on a first channel during first
period, and performing a second random backoff operation on a
second channel during a second period; performing a second random
backoff operation on the second link during a second period having
a different length as the first period; and in response to
determining that the first random backoff operation is completed
and the second random backoff operation is not completed,
performing a monitoring operation on the first channel while
performing the second random backoff operation; and in response to
determining that the first channel is in an idle state as a result
of the monitoring operation, and that the second random backoff
operation is completed, transmitting a first frame on the first
channel and a second frame on the second scheme, respectively, from
a first time point.
9. The operation method according to claim 8, wherein the first
period and the second period have different durations.
10. The operation method according to claim 9, wherein the first
period is determined based on an access category corresponding to
the first frame, and the second period is determined based on an
access category corresponding to the second frame.
11. The operation method according to claim 9, wherein each of the
first frame and the second frame is a physical layer protocol data
unit (PPDU).
12. The operation method according to claim 8, wherein padding
bit(s) are added to at least one of the first frame and the second
frame so that the first frame and the second frame have a same
duration.
13. The operation method according to claim 1, wherein the first
time point is a completion time point of the second random backoff
operation, and the transmission of the first frame and the
transmission of the second frame are started simultaneously at the
first time point.
14. A communication node in a wireless communication network, the
communication node comprising: at least one processor, a
transceiver controlled by the at least one processor, and a memory
storing instructions, wherein when executed by the at least one
processor, the instructions cause the communication node to:
perform, by using the transceiver, a first random backoff operation
on a first link during a first period, and perform, by using the
transceiver, a second random backoff operation on a second link
during a second period; in response to determining that the first
random backoff operation is completed and the second random backoff
operation is not completed, perform, by using the transceiver, a
monitoring operation on the first link while performing the second
random backoff operation; and in response to determining that the
first link is in an idle state as a result of the monitoring
operation, and that the second random backoff operation is
completed, transmit, by using the transceiver, a first frame on the
first link and a second frame on the second link, respectively,
from a first time point.
15. The communication node according to claim 14, wherein the first
period and the second period have different durations.
16. The communication node according to claim 15, wherein the first
period is determined based on an access category corresponding to
the first frame, and the second period is determined based on an
access category corresponding to the second frame.
17. The communication node according to claim 14, wherein each of
the first frame and the second frame is a physical layer protocol
data unit (PPDU).
18. The communication node according to claim 14, wherein padding
bit(s) are added to at least one of the first frame and the second
frame so that the first frame and the second frame have a same
duration delay transmission of.
19. The communication node according to claim 14, wherein the first
time point is a completion time point of the second random backoff
operation, and the transmission of the first frame and the
transmission of the second frame are started simultaneously at the
first time point.
20. The communication according to claim 14, wherein the
communication node is a non-simultaneous transmit and receive
(non-STR) multi-link device (MLD), and the communication node uses
different medium access control (MAC) layer addresses for the first
link and the second link.
Description
BACKGROUND
(A) Technical Field
[0001] The present disclosure relates to a communication method in
a broadband wireless communication network, more particularly, to a
method, an apparatus, and a system for frame transmission through a
random backoff operation according to characteristics of a frame
payload.
(b) Description of the Related Art
[0002] Recently, with the spread of mobile devices, wireless LAN
technology that can provide fast wireless Internet services to the
mobile devices has been in the spotlight. The standards for the
wireless LAN technology are being developed mainly as the IEEE
802.11 standards by the Institute of Electrical and Electronics
Engineers (IEEE). The IEEE 802.11 standards were developed and
standardized in such a way that, starting with the initial version
supporting 1 to 2 Mbps, they were revised through subsequent
versions.
[0003] Standardized technologies for specific operations such as
fast handoff (i.e., fast BSS transition), fast initial link setup,
technology for low-power terminals operating in a band of 1 GHz or
below, wireless LAN technology for vehicle terminals, and the like
were developed, and reflected in the respective standard revisions.
In particular, the wireless LAN technology for vehicle terminals is
reflected in the IEEE 802.11p, which is based on a signal form in
the IEEE 802.11a and an enhanced distributed channel access (EDCA)
in the IEEE 802.11e, and operates in a band of 5.9 GHz. Further, it
is based on a 10 MHz bandwidth to be suitable for a terminal having
high mobility, and supports `outside context of BSS (OCB)`
communication so that the terminal can directly perform
inter-vehicle communications without going through authentication
and association procedures with a wireless access point.
[0004] Meanwhile, as more sensors and operations are developed for
vehicle communication operations, applications for the
corresponding operations are diversified, and in order to achieve a
higher data throughput and improve a transmission distance compared
to the IEEE 802.11p, the IEEE 802.11bd is being developed and
standardized to establish a wireless LAN standard for
next-generation vehicle communication (i.e., next generation V2X
(NGV)).
[0005] Recently, as applications requiring a higher throughput and
applications requiring real-time transmission occur, an Extreme
High Throughput (EHT) wireless LAN technology has been proposed and
is under development.
SUMMARY
[0006] The present disclosure is directed to solving a capacity
problem of a 10 MHz channel, and provides methods for performing a
multi-random backoff operation according to an access class (AC) of
enhanced distributed channel access (EDCA), in which a 20 MHz
channel is used by extending the 10 MHz channel to the 20 MHz
channel in consideration of fairness with an adjacent 10 MHz
channel when the adjacent 10 MHz channel is available.
[0007] The present disclosure provides methods for transmitting
frames through one or more links by configuring a multi-link
association and performing a random backoff operation on each of a
plurality of links.
[0008] An operation method of a communication node in a wireless
communication network, according to an exemplary embodiment of the
present disclosure, may comprise: performing a first monitoring
operation on a first link and a second link during a preset period;
in response to determining that the first link and the second link
are in idle states as a result of the first monitoring operation,
performing a first random backoff operation on the first link
during a first random backoff period; performing a second random
backoff operation on the second link during a second random backoff
period; and in response to determining that the first link is in
idle state as a result of the first random backoff operation and
determining that the second link is in idle state as a result of
the second random backoff operation, transmitting a frame through
the first link and the second link at a same time.
[0009] The first link may be a primary link having a 10 MHz
bandwidth for transmitting the frame, and the second link may be a
secondary link having a 10 MHz bandwidth for extending the first
link.
[0010] The frame may include a 20 MHz physical layer convergence
procedure (PLCP) protocol data unit (PPDU).
[0011] The preset period may be an arbitration interframe space
(AIFS).
[0012] The operation method may further comprise, when the first
random backoff operation on the first link is completed, delaying
the transmission of the frame through the first link until
completion of the second random backoff operation.
[0013] In the delaying of the transmission of the frame through the
first link until completion of the second random backoff operation,
the transmission of the frame may be delayed when a difference
between the first random backoff period and the second random
backoff period is less than or equal to a preset value.
[0014] The performing of the first random backoff operation on the
first link further may comprise: detecting a busy state of the
first link by another communication node; and performing a second
monitoring operation on the first link during a preset point
coordination function (PIFS) period when the busy state of the
first link ends, wherein the frame is transmitted through the first
link and the second link, in response to determining that the first
link is in idle state as a result of the second monitoring
operation, and determining that the second link is in idle state as
a result of performing the second random backoff operation.
[0015] An operation method of a first communication node in a
wireless communication network, according to another exemplary
embodiment of the present disclosure, may comprise: establishing a
plurality of links including a first link and a second link with a
second communication node; performing a first random backoff
operation on the first link during a first period; transmitting a
sharing frame requesting occupation of the first link to the second
communication node through the first link, after completion of the
first random backoff operation; delaying transmission of a frame
during a busy period of the first link occupied by the second
communication node receiving the sharing frame; performing a second
random backoff operation on the second link during a second period
having a different length as the first period; and in response to
determining that the first link and the second link are in idle
states, transmitting the frame through the first link and the
second link at a same time.
[0016] The operation method may further comprise, after
transmitting the sharing frame to the second communication node,
receiving an acknowledgement (ACK) for the sharing frame from the
second communication node through the first link.
[0017] The ACK for the sharing frame may include information on
whether the second link is busy at a time of transmitting the
sharing frame.
[0018] The operation method may further comprise, after receiving
the ACK for the sharing frame, receiving a downlink frame from the
second communication node through the first link after a preset
time period elapses from a time of receiving the ACK for the
sharing frame.
[0019] The preset time period may be one of a point coordination
function interframe space (PIFS) or a short IFS (SIFS).
[0020] The operation method may further comprise, after the second
random backoff operation on the second link is completed,
receiving, from the second communication node, a trigger frame
indicating transmission of the frame, through the first link and
the second link.
[0021] The operation method may further comprise, after
transmitting the frame, receiving a block ACK (BA) for the frame
from the second communication node through the first link and the
second link.
[0022] A first communication node in a wireless communication
network, according to yet another exemplary embodiment of the
present disclosure, may comprise a processor; a memory storing at
least one instruction executable by the processor; and transmit
antennas for transmitting signals generated by the processor,
wherein the at least one instruction is executed to: establish a
plurality of links including a first link and a second link with a
second communication node; establish a plurality of links including
a first link and a second link with a second communication node;
perform a first monitoring operation on the first link and the
second link during a preset period; in response to determining that
the first link and the second link are in idle states as a result
of the first monitoring operation, perform a first random backoff
operation on the first link during a first random backoff period;
perform a second random backoff operation on the second link during
a second random backoff period; and in response to determining that
the first link is in idle state as a result of the first random
backoff operation and determining that the second link is in idle
state as a result of the second random backoff operation, transmit
a frame through the first link and the second link at a same
time.
[0023] The first link may be a primary link having a 10 MHz
bandwidth for transmitting the frame, the second link may be a
secondary link having a 10 MHz bandwidth for extending the first
link, and the frame may include a 20 MHz physical layer convergence
procedure (PLCP) protocol data unit (PPDU).
[0024] The at least one instruction may be further executed to:
after performing the first random backoff operation on the first
link, delay the transmission of the frame through the first link
until completion of the second random backoff operation when a
difference between the first random backoff period and the second
random backoff period is less than or equal to a preset value.
[0025] The at least one instruction may be further executed to:
after performing the first random backoff operation, transmit a
sharing frame requesting occupation of the first link to the second
communication node through the first link; receive an
acknowledgement (ACK) for the sharing frame from the second
communication node; and delay transmission of the frame during a
busy period of the first link occupied by the second communication
node receiving the sharing frame.
[0026] The at least one instruction may be further executed to:
after performing the second random backoff operation on the second
link, receive, from the second communication node, a trigger frame
indicating transmission of the frame, through the first link and
the second link.
[0027] The at least one instruction may be further executed to:
after transmitting the frame, receive a block ACK (BA) for the
frame from the second communication node through the first link and
the second link.
[0028] According to the present disclosure, a communication node
may perform a random backoff operation on each of configured
multi-links during a different period. Based on results of the
random backoff operations, the communication node may transmit
physical layer convergence procedure (PLCP) protocol data units
(PPDUs) the through a plurality of links.
[0029] According to the present disclosure, by dynamically
extending a channel or link according to a payload type and
performing transmission, a communication node transmitting a
real-time PPDU may transmit a frame after a small transmission
delay, and a communication node transmitting a non-real-time PPDU
may transmit the PPDU through a 20 MHz channel whenever
possible.
[0030] The present disclosure may be used in various communication
devices such as a communication node for a vehicle, a wireless
access point, and an access management device, and a station or
base station using cellular communication.
BRIEF DESCRIPTION OF DRAWINGS
[0031] FIG. 1 is a diagram illustrating a first exemplary
embodiment of a wireless LAN system.
[0032] FIG. 2 is a block diagram illustrating a first exemplary
embodiment of a communication node configured as a wireless LAN
system.
[0033] FIG. 3 is a sequence chart illustrating an association
procedure of a station in a wireless LAN system.
[0034] FIG. 4 is a timing diagram illustrating a first exemplary
embodiment of an operation method of a communication node based on
an EDCA.
[0035] FIG. 5 is a conceptual diagram illustrating an exemplary
embodiment of a communication network including communication nodes
performing vehicle-to-vehicle communication.
[0036] FIG. 6 is a conceptual diagram illustrating a first
exemplary embodiment of a method for allocating a channel and
defining a primary channel for a communication node performing
vehicle-to-vehicle communication.
[0037] FIG. 7 is a conceptual diagram illustrating an exemplary
embodiment of frame transmission through at least one channel of a
20 MHz channel extended based on a primary channel.
[0038] FIG. 8 is a conceptual diagram illustrating a first
exemplary embodiment of a frame transmission operation through a 20
MHz channel as a result of channel monitoring and random backoff
operation on a primary channel and a secondary channel.
[0039] FIG. 9 is a conceptual diagram illustrating a first
exemplary embodiment of a frame transmission operation through
dynamic channel extension as a result of channel monitoring and
random backoff operation on a primary channel and a secondary
channel.
[0040] FIG. 10 is a conceptual diagram illustrating a second
exemplary embodiment of a frame transmission operation through
dynamic channel extension as a result of channel monitoring and
random backoff operation on a primary channel and a secondary
channel.
[0041] FIG. 11 is a conceptual diagram illustrating a third
exemplary embodiment of a frame transmission operation through
dynamic channel extension as a result of channel monitoring and
random backoff operation on a primary channel and a secondary
channel.
[0042] FIG. 12 is a conceptual diagram illustrating a fourth
exemplary embodiment of a frame transmission operation through
dynamic channel extension as a result of channel monitoring and
random backoff operation on a primary channel and a secondary
channel.
[0043] FIG. 13 is a conceptual diagram illustrating an exemplary
embodiment of frame transmission through at least one channel as a
result of channel monitoring and random backoff operation on a
primary channel and a secondary channel.
[0044] FIG. 14 is a conceptual diagram illustrating a second
exemplary embodiment of a frame transmission operation through a 20
MHz channel as a result of channel monitoring and random backoff
operation on a primary channel and a secondary channel.
[0045] FIG. 15 is a conceptual diagram illustrating an exemplary
embodiment of a structure of a multi-link established between an AP
and a STA of a communication node.
[0046] FIG. 16 is a conceptual diagram illustrating a first
exemplary embodiment of a frame transmission operation through at
least one link among a plurality of links as a result of random
backoff operations on the plurality of links.
[0047] FIG. 17 is a conceptual diagram illustrating a second
exemplary embodiment of a frame transmission operation through at
least one link among a plurality of links as a result of random
backoff operations on the plurality of links.
[0048] FIG. 18 is a conceptual diagram illustrating a third
exemplary embodiment of a frame transmission operation through at
least one link among a plurality of links as a result of random
backoff operations on the plurality of links.
[0049] FIG. 19 is a conceptual diagram illustrating a fourth
exemplary embodiment of a frame transmission operation through at
least one link among a plurality of links as a result of random
backoff operations on the plurality of links.
[0050] FIG. 20 is a conceptual diagram illustrating an exemplary
embodiment of a structure of a sharing frame transmitted by a first
communication node.
[0051] FIG. 21 is a conceptual diagram illustrating an exemplary
embodiment of a structure of an ACK frame for a sharing frame.
[0052] FIG. 22A is a conceptual diagram illustrating a fifth-first
exemplary embodiment of a frame transmission operation through at
least one link among a plurality of links as a result of random
backoff operations on the plurality of links.
[0053] FIG. 22B is a conceptual diagram illustrating a fifth-second
exemplary embodiment of a frame transmission operation through at
least one link among a plurality of links as a result of random
backoff operations on the plurality of links.
[0054] FIG. 22C is a conceptual diagram illustrating a fifth-third
exemplary embodiment of a frame transmission operation through at
least one link among a plurality of links as a result of random
backoff operations on the plurality of links.
[0055] FIG. 23 is a conceptual diagram illustrating a sixth
exemplary embodiment of a frame transmission operation through at
least one link among a plurality of links as a result of random
backoff operations on the plurality of links.
[0056] FIG. 24A is a conceptual diagram illustrating a
seventh-first exemplary embodiment of a frame transmission
operation through at least one link among a plurality of links as a
result of random backoff operations on the plurality of links.
[0057] FIG. 24B is a conceptual diagram illustrating a
seventh-second exemplary embodiment of a frame transmission
operation through at least one link among a plurality of links as a
result of random backoff operations on the plurality of links.
[0058] FIG. 24C is a conceptual diagram illustrating a
seventh-third exemplary embodiment of a frame transmission
operation through at least one link among a plurality of links as a
result of random backoff operations on the plurality of links.
[0059] FIG. 25 is a conceptual diagram illustrating an eighth
exemplary embodiment of a frame transmission operation through at
least one link among a plurality of links as a result of random
backoff operations on the plurality of links.
[0060] FIG. 26A is a conceptual diagram illustrating a ninth-first
exemplary embodiment of a frame transmission operation through at
least one link among a plurality of links as a result of random
backoff operations on the plurality of links.
[0061] FIG. 26B is a conceptual diagram illustrating a ninth-second
exemplary embodiment of a frame transmission operation through at
least one link among a plurality of links as a result of random
backoff operations on the plurality of links.
DETAILED DESCRIPTION
[0062] Since the present disclosure may be variously modified and
have several forms, specific exemplary embodiments will be shown in
the accompanying drawings and be described in detail in the
detailed description. It should be understood, however, that it is
not intended to limit the present disclosure to the specific
exemplary embodiments but, on the contrary, the present disclosure
is to cover all modifications and alternatives falling within the
spirit and scope of the present disclosure.
[0063] Relational terms such as first, second, and the like may be
used for describing various elements, but the elements should not
be limited by the terms. These terms are only used to distinguish
one element from another. For example, a first component may be
named a second component without departing from the scope of the
present disclosure, and the second component may also be similarly
named the first component. The term "and/or" means any one or a
combination of a plurality of related and described items.
[0064] When it is mentioned that a certain component is "coupled
with" or "connected with" another component, it should be
understood that the certain component is directly "coupled with" or
"connected with" to the other component or a further component may
be disposed therebetween. In contrast, when it is mentioned that a
certain component is "directly coupled with" or "directly connected
with" another component, it will be understood that a further
component is not disposed therebetween.
[0065] The terms used in the present disclosure are only used to
describe specific exemplary embodiments, and are not intended to
limit the present disclosure. The singular expression includes the
plural expression unless the context clearly dictates otherwise. In
the present disclosure, terms such as `comprise` or `have` are
intended to designate that a feature, number, step, operation,
component, part, or combination thereof described in the
specification exists, but it should be understood that the terms do
not preclude existence or addition of one or more features,
numbers, steps, operations, components, parts, or combinations
thereof.
[0066] Unless otherwise defined, all terms (including technical and
scientific terms) used herein have the same meaning as commonly
understood by one of ordinary skill in the art to which this
disclosure belongs. Terms that are generally used and have been in
dictionaries should be construed as having meanings matched with
contextual meanings in the art. In this description, unless defined
clearly, terms are not necessarily construed as having formal
meanings.
[0067] Hereinafter, forms of the present disclosure will be
described in detail with reference to the accompanying drawings. In
describing the disclosure, to facilitate the entire understanding
of the disclosure, like numbers refer to like elements throughout
the description of the figures and the repetitive description
thereof will be omitted.
[0068] A wireless communication network to which exemplary
embodiments according to the present disclosure are applied will be
described. The wireless communication network to which the
exemplary embodiments according to the present disclosure are
applied is not limited to the contents described below, and the
exemplary embodiments according to the present disclosure may be
applied to various wireless communication networks.
[0069] FIG. 1 is a diagram illustrating a first exemplary
embodiment of a wireless LAN system.
[0070] As shown in FIG. 1, a wireless LAN system may include at
least one basic service set (BSS). The BSS denotes a set of
stations (STAs) (e.g., STA1, STA2 (i.e., AP1), STA3, STA4, and STA5
(i.e., AP2), STA6, STA7, and STA8) configured to communicate with
each other through successful synchronization. The BSS does not
necessarily denote a specific area. In exemplary embodiments below,
a station that performs a function of an access point may be
referred to as an "access point (AP)", and a station that does not
perform the function of an access point may be referred to as a
"non-AP station" or "station".
[0071] The BSSs may be classified into infrastructure BSSs and
independent BSSs (IBSSs). In particular, a BSS1 and a BSS2 may be
infrastructure BSSs, and a BSS3 may be an IBSS. The BSS1 may
include a first station STA1, a first access point STA2 (AP1)
providing a distribution service, and a distribution system (DS)
connecting a plurality of access points (i.e., STA2 (AP1), STA5
(AP2)). In the BSS1, the first AP (STA2 (AP1)) may manage the first
station STA1.
[0072] The BSS2 may include a third station STA3, a fourth station
(STA4), a second access point (STA5 (AP2)) providing a distribution
service, and a distribution system (DS) connecting a plurality of
access points (i.e., STA2 (AP1), STA5 (AP2)). In the BSS2, the
second AP (STA5 (AP2)) may manage the third station STA3 and the
fourth station STA4.
[0073] The BSS3 may be an IBSS operating in an ad-hoc mode. In the
BSS3, there is not an AP that is a centralized management entity
performing management functions at a center. In other words, in the
BSS3, the stations STA6, STA7, and STA8 may be managed in a
distributed manner. In the BSS3, all the stations STA6, STA7, and
STA8 may be mobile stations and may be not permitted to connect to
the DS, thus forming a self-contained network.
[0074] The access points (STA2 (AP1), STA5 (AP2)) may provide
access to the DS via a wireless medium for the stations STA1, STA3,
and STA4 associated therewith. In the BSS1 or BSS2, communication
between the stations STA1, STA3, and STA4 may be generally
performed through the access points (STA2 (AP1), STA5 (AP2)), but
when direct links are established, direct communication between the
stations STA1, STA3, and STA4 may be possible.
[0075] A plurality of infrastructure BSSs may be interconnected via
a DS. A plurality of BSSs connected via a DS is referred to as an
extended service set (ESS). The stations (e.g., STA1, STA2 (i.e.,
AP1), STA3, STA4, and STA5 (i.e., AP2)) included in an ESS may be
configured to communicate with each other, and a station (e.g.,
STA1, STA3, or STA4) in the ESS may move from one BSS to another
BSS while performing seamless communication.
[0076] The DS is a mechanism for one access point to communicate
with another access point. Using the DS, the access point may
transmit frames for stations associated with a BSS it manages, or
may transmit frames to stations having moved to another BSS. In
addition, the access point may transmit and receive frames to and
from an external network such as a wired network. Such the DS may
not necessarily have to be a network, and if it can provide a
predetermined distribution service specified in the IEEE 802.11
standard, there is no restriction on its form. For example, the DS
may be a wireless network such as a mesh network or a physical
structure that connects access points to each other.
[0077] Stations (i.e., communication nodes) of a wireless LAN
vehicle-to-everything (V2X) network may not perform operations of
configuring a BSS by synchronizing with an access point. The
stations (i.e., communication nodes) of the wireless LAN vehicle
communication network may perform `Outside the Context of BSS
(OCB)` communication for direct communication between the
station(s). Each of the stations performing OCB communication may
transmit a frame to other station(s) while omitting a procedure for
synchronization with the access point.
[0078] Each of the communication nodes (e.g., STA1, STA2 (AP1),
STA3, STA4, STA5 (AP2), STA6, STA7, and STA8) included in the
wireless LAN system may be configured as follows.
[0079] FIG. 2 is a block diagram illustrating a first exemplary
embodiment of a communication node configured as a wireless LAN
system.
[0080] As shown in FIG. 2, a communication node 200 may include at
least one processor 210, a memory 220, and a transceiver 230
connected to a network for performing communications. The
transceiver 230 may also be referred to as a "radio frequency (RF)
unit", "RF module", or the like. Additionally, the communication
node 200 may further include an input interface device 240, an
output interface device 250, a storage device 260, and the like.
Each component included in the communication node 200 may be
configured to communicate with each other as connected via a common
bus 270.
[0081] However, each of the components included in the
communication node 200 may be connected to the processor 210 via a
separate interface or a separate bus rather than the common bus
270. For example, the processor 210 may be connected to at least
one of the memory 220, the transceiver 230, the input interface
device 240, the output interface device 250, and the storage device
260 via a dedicated interface.
[0082] The processor 210 may be configured to execute at least one
instruction stored in at least one of the memory 220 and the
storage device 260. The processor 210 may refer to a central
processing unit (CPU), a graphics processing unit (GPU), or a
dedicated processor. Methods in accordance with exemplary
embodiments of the present disclosure may be performed by the
processor 210. Each of the memory 220 and the storage device 260
may include at least one of a volatile storage medium and a
non-volatile storage medium. For example, the memory 220 may
include at least one of read-only memory (ROM) and random access
memory (RAM).
[0083] Meanwhile, in the wireless LAN system, an association
procedure may be performed as follows.
[0084] FIG. 3 is a sequence chart illustrating an association
procedure of a station in a wireless LAN system.
[0085] As shown in FIG. 3, an association procedure of a station
STA in an infrastructure BSS may generally be divided into a probe
step of probing an AP, an authentication step for authentication
with the probed AP, and an association step of associating with the
authenticated AP.
[0086] The STA may discover neighboring APs. The STA may transmit a
probe request frame, and may detect neighboring APs by receiving
probe response frames that are responses to the probe request frame
from the neighboring APs. The STA may exchange information on
whether a multi-link association is possible and information on
available links with the AP.
[0087] The STA may perform the association step with the AP. That
is, the STA may transmit an association request frame to the
selected AP, and may complete association with the selected AP by
receiving, from the selected AP, an association response frame that
is a response to the association request frame.
[0088] The STA may perform a negotiation procedure for multi-link
association with the AP in the association step with the AP. The AP
may allocate information of available links of the AP and an
identifier (ID) to each of the links and, and may transmit
information on whether each of the links is activated or not by
using the ID in the negotiation and change procedure for multi-link
operation.
[0089] The STA may exchange information on availability of the
multi-link operation by exchanging capability elements (e.g., EHT
capability elements) with the AP. The capability elements may
include a supported band, information of supported links, the
number of supported links, information on a band interval between
bands for a communication node (e.g., STA and AP) to support
simultaneous transmission/reception operations, and the like.
[0090] The STA having performed the association step with the AP
may configure a multi-link association with the AP. That is, the
STA may transmit a multi-link request frame to the AP, and may
complete configuration of the multi-link association with the
selected AP by receiving, from the selected AP, a multi-link
response frame that is a response to the multi-link request
frame.
[0091] In the case of wireless LAN V2X communication, the stations
(i.e., communication nodes) may not need to perform operations of
configuring a BSS by synchronizing with an AP, and may perform OCB
communication for direct communication between the station(s). Each
of the stations performing OCB communication may transmit a frame
to other station(s) while omitting a beacon reception procedure for
discovering an AP and synchronizing with the AP, probe
request/response procedure, association request/response procedure,
authentication procedure, and the like.
[0092] Meanwhile, a communication node (e.g., access point,
station, etc.) belonging to the WIRELESS LAN system may be
configured to perform transmission and reception of a frame based
on a point coordination function (PCF), a hybrid coordination
function (HCF), an HCF controlled channel access (HCCA), a
distributed coordination function (DCF), and/or an enhanced
distributed channel access (EDCA).
[0093] The frame in the WIRELESS LAN system may be classified into
a management frame, a control frame, and a data frame. The
management frame may be classified into an association request
frame, an association response frame, a reassociation request
frame, a reassociation response frame, a probe request frame, a
probe response frame, a beacon frame, and an association.
Additionally, the management frame may include a disassociation
frame, an authentication frame, a deauthentication frame, an action
frame, and the like.
[0094] The control frame may be classified into an acknowledgment
(ACK) frame, a block ACK request (BAR) frame, a block ACK (BA)
frame, a power saving (PS)-Poll frame, a request-to-send (RTS)
frame, a clear-to-send (CTS) frame, and the like. The data frame
may be classified into a quality of service (QoS) data frame and a
non-QoS data frame. The QoS data frame may refer to a data frame
for transmission based on the QoS, and the non-QoS data frame may
refer to a data frame for transmission not based on the QoS.
[0095] Meanwhile, in the wireless LAN system, a communication node
(e.g., access point or station) may be configured to operate based
on the EDCA.
[0096] FIG. 4 is a timing diagram illustrating a first exemplary
embodiment of an operation method of a communication node based on
an EDCA.
[0097] As shown in FIG. 4, a communication node intending to
transmit a control frame (or management frame) may be configured to
perform a monitoring operation (e.g., carrier sensing operation) on
a channel state during a predetermined period (e.g., short
interframe space (SIFS) or PCF IFS (PIFS)). When the channel state
is determined to be idle during the predetermined period (e.g.,
SIFS or PIFS), the communication node may be configured to transmit
a control frame (or management frame). For example, the
communication node may be configured to transmit an ACK frame, a BA
frame, a CTS frame, or the like when the channel state is
determined to be idle during an SIFS. Additionally, the
communication node may be configured to transmit a beacon frame or
the like when the channel state is determined to be idle during a
PIFS. When the channel state is determined to be busy during the
predetermined period (e.g., SIFS or PIFS), the communication node
may be configured not to transmit a control frame (or management
frame). In particular, the carrier sensing operation may be
referred to as a clear channel assessment (CCA) operation.
[0098] A communication node intending to transmit a non-QoS data
frame may be configured to perform a monitoring operation (e.g.,
carrier sensing operation) on a channel state during a DCF IFS
(DIFS). When the channel state is determined to be idle during a
DIFS, the communication node may be configured to perform a random
backoff procedure. For example, the communication node may be
configured to select a backoff value (e.g., backoff counter) within
a contention window based on the random backoff procedure, and
perform the monitoring operation (e.g., carrier sensing operation)
during a period corresponding to the selected backoff value. The
communication node may be configured to transmit a non-QoS data
frame when the channel state is determined to be idle during the
backoff period.
[0099] A communication node intending to transmit a QoS data frame
may be configured to perform a monitoring operation (e.g., carrier
sensing operation) on a channel state during an arbitration IFS
(AIFS). When the channel state is determined to be idle during an
AIFS, the communication node may be configured to perform a random
backoff procedure. The AIFS may be set based on an access category
(AC) of a data unit (e.g., protocol data unit (PDU)) included in
the QoS data frame. The AC of the data unit may be as shown in
Table 1 below.
TABLE-US-00001 TABLE 1 Priority AC Description Lowest AC_BK
Background . AC_BE Best effort . AC_VI Video . AC_VO Voice
Highest
[0100] AC_BK may indicate background data, AC_BE may indicate data
transmitted in a best effort manner, AC_VI may indicate video data,
and AC_VO may indicate voice data. For example, the length of the
AIFS for the QoS data frame of each of AC_VO and AC_VI may be set
equal to the length of the DIFS. The length of the AIFS for the QoS
data frame of AC_BE and AC_BK may be set longer than the length of
the DIFS. The length of the AIFS for the QoS data frame of AC_BK
may be set longer than the length of the AIFS for the QoS data
frame of AC_BE.
[0101] In the random backoff procedure, the communication node may
be configured to select a backoff value (e.g., backoff counter)
within a contention window based on the AC of the QoS data frame.
The contention window based on the AC may be as shown in Table 2
below. As shown below, CW.sub.min may indicate the minimum value of
the contention window, CW.sub.max may indicate the maximum value of
the contention window, and each of the minimum and maximum values
of the contention window may be expressed by the number of
slots.
TABLE-US-00002 TABLE 2 AC CW.sub.min CW.sub.max AC_BK 31 1023 AC_BE
31 1023 AC_VI 15 31 AC_VO 7 15
[0102] The communication node may be configured to perform a
monitoring operation (e.g., carrier sensing operation) on the
channel state during a backoff period, and transmit the QoS data
frame when the channel state is determined to be idle during the
backoff period.
[0103] Hereinafter, wireless LAN multi-channel operation methods in
a communication system will be described. Even when a method (e.g.,
transmission or reception of a signal) to be performed at a first
communication node among communication nodes is described, a
corresponding second communication node may be configured to
perform a method (e.g., reception or transmission of the signal)
corresponding to the method performed at the first communication
node. In other words, when an operation of a non-AP station is
described, the corresponding AP may be configured to perform an
operation that corresponds to the operation of the non-AP station.
Conversely, when an operation of the AP is described, the
corresponding non-AP station may be configured to perform an
operation that corresponds to the operation of the AP.
[0104] FIG. 5 is a conceptual diagram illustrating an exemplary
embodiment of a communication network including communication nodes
performing vehicle-to-vehicle communication.
[0105] As shown in FIG. 5, when a vehicle communication node
including a communication device detects a specific situation
through a sensor or performs a specific operation, the vehicle
communication node may transmit and receive data including a
position, speed, acceleration, and measurement result of the sensor
of a vehicle in form of a broadcast frame. In addition, the vehicle
communication node may receive a map of the surrounding situation
and information on a specific event (e.g., accident and congestion
information in the direction of road travel, etc.) from a roadside
device such as a street light, traffic light, or the like on the
road. The communication node in the vehicle communication network
environment may not perform scanning, authentication, and
association operations performed in the conventional WIRELESS LAN
operation, and may transmit and receive OCB data without belonging
to a specific BSS. Accordingly, a periodic beacon frame
transmission operation or the like from a wireless access point may
not be performed.
[0106] FIG. 6 is a conceptual diagram illustrating a first
exemplary embodiment of a method for allocating a channel and
defining a primary channel for a communication node performing
vehicle-to-vehicle communication.
[0107] As shown in (a) of FIG. 6, in case of the United States, a
channel of a 5.9 GHz band for vehicle communication is defined as a
band of 5.850 GHz to 5.925 GHz band, of which a channel 178 (5.885
GHz to 5.895 GHz) may be used for a control channel for
transmitting control information or broadcasting use of another
channel. Among the channels, a channel 172 may be a channel only
for transmission of a safety message between vehicle communication
nodes, and a channel 184 may be a channel allocated to extend a
transmission distance of a frame. Accordingly, channels that can be
used for 20 MHz bandwidth transmission may belong to a band of
5.865 GHz to 5.885 GHz or a band of 5.895 GHz to 5.915 GHz.
[0108] In order to transmit data at a high data rate using a 20 MHz
bandwidth, as utilized in the existing WIRELESS LAN standard (IEEE
802.11n or IEEE 802.11ac), the communication node may transmit a
frame by extending a bandwidth based on a primary channel. When the
communication node extends a bandwidth based on the primary
channel, the communication node may preconfigure the primary
channel.
[0109] According to an exemplary embodiment, a communication node
may fixedly configure a part of a band used for 20 MHz bandwidth
communication as a primary channel. For example, if the
communication node uses a band of 5.865 GHz to 5.885 GHz to
transmit a signal having 20 MHz bandwidth, the communication node
may fix a channel 174 (i.e., 5.865 GHz-5.875 GHz) as the primary
channel to perform control channel access and frame transmission
operations. When all vehicle communication nodes use the same
primary channel, the communication node may basically recognize one
channel (e.g., channel 174) among radio resources of 20 MHz
bandwidth as the primary channel, and may sense the primary
channel. In addition, the communication node performing the channel
access operation may decode a frame by detecting the frame received
through the 20 MHz channel as a result of sensing the primary
channel or by detecting the frame received through the primary
channel.
[0110] When intending to transmit a 20 MHz bandwidth signal by
changing the primary channel of the corresponding band, the
communication node may broadcast information on whether the primary
channel is changed to the other communication nodes by a method
utilizing a protocol in the upper layer (e.g., the method of
indicating a primary channel together when a CCH indicates a
channel to be used in a next period as in the existing IEEE
1609.4).
[0111] As shown in (b) of FIG. 6, in order to minimize the
disadvantage that a communication node of one channel continuously
suffers losses due to the fixed primary channel configuration as in
(a) of FIG. 7, the communication node may not fixedly designate one
primary channel, and may configure the primary channel randomly.
The communication node may randomly configure one primary channel
whenever channel access is performed by extending a bandwidth to 20
MHz, and may transmit a frame through the configured primary
channel. Alternatively, the communication node may change
configuration of the primary channel whenever performing channel
access for transmitting a 20 MHz bandwidth signal. For example,
when transmitting a frame through channels 174 and 176, the
communication node may configure the channel 174 as the primary
channel when transmitting the first frame, and may configure the
channel 176 as the primary channel when transmitting the next
frame. Even when the communication node transmits frames through
the channels 180 and 182, the communication node may change the
channel configuration by applying the same scheme. When
communication nodes configure the primary channels randomly or
alternately, the communication node receiving the frame from other
communication nodes cannot identify the primary channel among the
two channels in advance, so that the communication node may sense
each 10 MHz channel constituting the 20 MHz bandwidth channel.
[0112] FIG. 7 is a conceptual diagram illustrating an exemplary
embodiment of frame transmission through at least one channel of a
20 MHz channel extended based on a primary channel.
[0113] As shown in FIG. 7, a communication node may transmit a
frame through a radio resource having a bandwidth extended to 20
MHz. The radio resource having a bandwidth extended to 20 MHz may
include two channels (e.g., channel 174 and channel 176), and each
of the two channels for frame transmission may include a primary
channel and a secondary channel adjacent to the primary channel.
For example, the primary channel among the two channels for frame
transmission may be the channel 174, and the secondary channel may
be the channel 176. In order to transmit a frame through the radio
resource having a 20 MHz bandwidth, the communication node may
perform access to the primary channel.
[0114] The communication node may perform a random backoff
operation for channel access to the primary channel, and may
perform a channel monitoring operation on the secondary channel
during a preset time period. The length of the preset time period
may be a PIFS, and the ending time of the PIFS may be the same as
the time of completing the random backoff operation on the primary
channel. According to the exemplary embodiment of (a) of FIG. 7, if
the shorter backoff operation period in the primary channel ends
and the secondary channel is in the idle state during the PIFS time
period as a result of the channel monitoring on the secondary
channel, the communication node may immediately transmit a frame
through the primary channel and the secondary channel. On the other
hand, according to the exemplary embodiment of (b) of FIG. 7, if
the secondary channel is in the busy state during the PIFS time
period as a result of the channel monitoring on the secondary
channel, the communication node may not transmit a frame through
the secondary channel, and may transmit the frame only through the
primary channel. The communication node may transmit a frame to be
transmitted through a 20 MHz channel only through the primary
channel that is a 10 MHz channel, and such the frame transmission
operation through the 10 MHz channel may be referred to as
`fallback transmission`.
[0115] FIG. 8 is a conceptual diagram illustrating a first
exemplary embodiment of a frame transmission operation through a 20
MHz channel as a result of channel monitoring and random backoff
operation on a primary channel and a secondary channel.
[0116] As shown in FIG. 8, a communication node may transmit a
frame through two channels (e.g., channel 174 and channel 176). One
channel (e.g., channel 174) of the two channels for frame
transmission may be a primary channel, and the other channel (e.g.,
channel 176) may be a secondary channel for extension of the
primary channel.
[0117] The communication node may monitor the channels (e.g.,
primary channel and/or secondary channel) before transmitting a
real-time frame (e.g., frame including a video and/or voice
payload, etc.). According to the exemplary embodiment of FIG. 8,
the communication node may identify whether the channels are busy
by monitoring the channels (e.g., primary channel and/or secondary
channel) during a preset AIFS time period. According to the
exemplary embodiment of FIG. 8, the communication node may
determine whether the channels (e.g., primary channel and secondary
channel) are busy during the preset AIFS time period.
[0118] As a result of the channel monitoring, if the channels
(e.g., primary channel and secondary channel) are not busy during
the preset AIFS time period, the communication node may perform
random backoff operations on the channels. The communication node
may independently perform the random backoff operation on each of
the channels. That is, the communication node may perform the
random backoff operation on the primary channel during a first
period, and may perform the random backoff operation on the
secondary channel during a second period. The first period may be a
period having a length different from that of the second period. In
order to determine the first period and the second period, the
communication node may select random backoff counter values
according to a rule set for each access category (AC) according to
a type of a frame to be transmitted when performing the random
backoffs. The communication node may randomly select two random
backoff counters to be applied respectively to the first period and
the second period at the same time. In a specific exemplary
embodiment, the first and second periods may be AC_VO or AC_VI of
FIG. 4. When the communication node completes the random backoff
operations on the channels (e.g., primary channel and secondary
channel), the communication node may transmit a 20 MHz PPDU frame
through the primary channel and the secondary channel. That is, the
communication node may transmit the frame through all available
channels. The 20 MHz PPDU may be a plurality of PPDUs each of which
is independent for each 10 MHz channel. The communication node may
terminate the PPDU transmission through all channels at the same
time. Therefore, if data bits of a PPDU are too small to end the
transmissions of the PPDUs at the same time, the communication node
may add padding bits to the PPDU to match the ending times of the
PPDUs, thereby ending the transmissions of the PPDUs at the same
time.
[0119] FIG. 9 is a conceptual diagram illustrating a first
exemplary embodiment of a frame transmission operation through a 20
MHz band channel as a result of channel monitoring and random
backoff operation on a primary channel and a secondary channel.
[0120] As shown in FIG. 9, a communication node may transmit a
frame through two channels (e.g., channel 174 and channel 176). One
channel (e.g., channel 174) of the two channels for frame
transmission may be a primary channel, and the other channel (e.g.,
channel 176) may be a secondary channel for extension of the
primary channel.
[0121] The communication node may monitor the channels (e.g.,
primary channel and/or secondary channel) before transmitting a
real-time frame (e.g., frame including a video and/or voice
payload, etc.). According to the exemplary embodiment of FIG. 9,
the communication node may identify whether the channels are busy
by monitoring the channels (e.g., primary channel and/or secondary
channel) during a preset AIFS time period.
[0122] As a result of the channel monitoring, if the channels
(e.g., primary channel and secondary channel) are not busy during
the preset AIFS time period, the communication node may perform
random backoff operations on the channels. The communication node
may independently perform the random backoff operation on each of
the channels. That is, the communication node may perform the
random backoff operation on the primary channel during a first
period, and may perform the random backoff operation on the
secondary channel during a second period. The first period may be a
period having a length different from that of the second
period.
[0123] If the communication node completes the random backoff
operation on the primary channel, but detects a busy state of the
secondary channel, the communication node may perform fallback
transmission of a 10 MHz PPDU frame through the primary
channel.
[0124] FIG. 10 is a conceptual diagram illustrating a second
exemplary embodiment of a frame transmission operation through
dynamic channel extension as a result of channel monitoring and
random backoff operation on a primary channel and a secondary
channel.
[0125] As shown in FIG. 10, a communication node may transmit a
frame through two channels (e.g., channel 174 and channel 176). One
channel (e.g., channel 174) of the two channels for frame
transmission may be a primary channel, and the other channel (e.g.,
channel 176) may be a secondary channel for extension of the
primary channel.
[0126] The communication node may monitor the channels (e.g.,
primary channel and/or secondary channel) before transmitting a
real-time frame (e.g., frame including a video and/or voice
payload, etc.). According to the exemplary embodiment of FIG. 10,
the communication node may identify whether the channels are busy
by monitoring the channels (e.g., primary channel and/or secondary
channel) during a preset AIFS time period.
[0127] As a result of the channel monitoring, if the channels
(e.g., primary channel and secondary channel) are not busy during
the preset AIFS time period, the communication node may perform
random backoff operations on the channels. The communication node
may independently perform the random backoff operation on each of
the channels. That is, the communication node may perform the
random backoff operation on the primary channel during a first
period, and may perform the random backoff operation on the
secondary channel during a second period. The first period may be a
period having a length different from that of the second
period.
[0128] The communication node may complete the random backoff
operation on the secondary channel. In addition, the communication
node may further perform the random backoff operation on the
primary channel even after completing the random backoff operation
on the secondary channel. If the communication node detects a busy
state of the secondary channel after completing the random back-off
operation on the secondary channel, the communication node may
perform monitoring on the primary channel during a PIFS time period
from the time of detecting the busy state of the secondary channel,
in addition to the random backoff operation on the primary
channel.
[0129] As a result of the channel monitoring, after the
communication node completes the random backoff operation during
the second period, if the secondary channel is occupied by another
communication node and the primary channel is not busy during the
PIFS time period, the communication node may perform fallback
transmission of a 10 MHz PPDU frame through the primary
channel.
[0130] FIG. 11 is a conceptual diagram illustrating a third
exemplary embodiment of a frame transmission operation through
dynamic channel extension as a result of channel monitoring and
random backoff operation on a primary channel and a secondary
channel.
[0131] As shown in FIG. 11, a communication node may transmit a
frame through two channels (e.g., channel 174 and channel 176). One
channel (e.g., channel 174) of the two channels for frame
transmission may be a primary channel, and the other channel (e.g.,
channel 176) may be a secondary channel for extension of the
primary channel.
[0132] The communication node may monitor the channels (e.g.,
primary channel and/or secondary channel) before transmitting a
real-time frame (e.g., frame including a video and/or voice
payload, etc.). According to the exemplary embodiment of FIG. 11,
the communication node may identify whether the channels are busy
by monitoring the channels (e.g., primary channel and/or secondary
channel) during a preset AIFS time period.
[0133] As a result of the channel monitoring, if the channels
(e.g., primary channel and secondary channel) are not busy during
the preset AIFS time period, the communication node may perform
random backoff operations on the channels. The communication node
may independently perform the random backoff operation on each of
the channels. That is, the communication node may perform the
random backoff operation on the primary channel during a first
period, and may perform the random backoff operation on the
secondary channel during a second period. The first period may be a
period having a length different from that of the second
period.
[0134] The communication node may detect a busy state of the
primary channel. Specifically, the communication node may detect
the busy state of the primary channel before the completion of the
random backoff operation on the secondary channel. In addition, the
communication node may complete the random backoff operation on the
secondary channel. When the communication node completes the random
backoff operation on the secondary channel, the communication node
may perform fallback transmission of a 10 MHz PPDU frame through
the secondary channel.
[0135] FIG. 12 is a conceptual diagram illustrating a fourth
exemplary embodiment of a frame transmission operation through
dynamic channel extension as a result of channel monitoring and
random backoff operation on a primary channel and a secondary
channel.
[0136] As shown in FIG. 12, a communication node may transmit a
frame through two channels (e.g., channel 174 and channel 176). One
channel (e.g., channel 174) of the two channels for frame
transmission may be a primary channel, and the other channel (e.g.,
channel 176) may be a secondary channel for extension of the
primary channel.
[0137] The communication node may monitor the channels (e.g.,
primary channel and/or secondary channel) before transmitting a
real-time frame (e.g., frame including a video and/or voice
payload, etc.). According to the exemplary embodiment of FIG. 12,
the communication node may identify whether the channels are busy
by monitoring the channels (e.g., primary channel and/or secondary
channel) during a preset AIFS time period.
[0138] As a result of the channel monitoring, if the channels
(e.g., primary channel and secondary channel) are not busy during
the preset AIFS time period, the communication node may perform
random backoff operations on the channels. The communication node
may independently perform the random backoff operation on each of
the channels. That is, the communication node may perform the
random backoff operation on the primary channel during a first
period, and may perform the random backoff operation on the
secondary channel during a second period. The first period may be a
period having a length different from that of the second
period.
[0139] The communication node may complete the random backoff
operation on the secondary channel. In addition, the communication
node may further perform the random backoff operation on the
primary channel even after completing the random backoff operation
on the secondary channel. If the communication node detects a busy
state of the primary channel after completing the random backoff
operation on the secondary channel, the communication node may
perform monitoring on the secondary channel during a PIFS time
period from the time of detecting the busy state of the primary
channel, in addition to the random backoff operation on the primary
channel.
[0140] As a result of the channel monitoring, after the
communication node completes the random backoff operation during
the second period, if the primary channel is occupied by another
communication node and the secondary channel is not busy during the
PIFS time period, the communication node may perform fallback
transmission of a 10 MHz PPDU frame through the secondary
channel.
[0141] FIG. 13 is a conceptual diagram illustrating an exemplary
embodiment of frame transmission through at least one channel as a
result of channel monitoring and random backoff operation on a
primary channel and a secondary channel.
[0142] As shown in FIG. 13, the communication node may transmit a
frame through two channels (e.g., channel 174 and channel 176).
Hereinafter, the channel 174 may be referred to as a first channel,
and the channel 176 may be referred to as a second channel.
[0143] The communication node may perform monitoring on the
channels (e.g., the first channel and/or the second channel) before
transmitting a non-real-time frame (e.g., frame including a best
effort and/or background payload, etc.). According to the exemplary
embodiment of FIG. 13, when one channel among the channels is
occupied by another communication node, the communication node may
wait until the busy state of the occupied one channel ends.
[0144] When the one occupied channel transitions from the busy
state to the idle state, the communication node may identify
whether the channels (e.g., the first channel and the second
channel) are busy by monitoring the channels during a preset AIFS
time period.
[0145] As a result of the channel monitoring, if the channels
(e.g., primary channel and secondary channel) are not busy during
the preset AIFS time period, the communication node may perform
random backoff operations on the channels. The communication node
may independently perform the random backoff operation on each of
the channels. That is, the communication node may perform the
random backoff operation on the primary channel during a first
period, and may perform the random backoff operation on the
secondary channel during a second period. The first period may be a
period having a length different from that of the second period.
The communication node may determine a primary channel among the
channels by comparing the lengths of the first period and the
second period. As in the exemplary embodiment of FIG. 13, when the
first period is longer than the second period, the communication
node may configure the second channel as a primary channel and
configure the first channel as a secondary channel.
[0146] The communication node may perform a random backoff
operation for channel access on the primary channel (e.g., the
second channel) and may perform a random backoff operation on the
secondary channel (e.g., the first channel). In addition, the
communication node may perform a channel monitoring operation on
the secondary channel during a preset time period. The length of
the preset time period may be a PIFS, and the ending time of the
PIFS may be the same as the time of completing the random backoff
operation on the primary channel. According to the exemplary
embodiment of (a) of FIG. 13, if the communication node completes
the second random backoff operation on the primary channel, and at
the same time, the secondary channel is in the idle state during
the PIFS time period as a result of the channel monitoring on the
secondary channel, the communication node may immediately transmit
a frame through the primary and secondary channels. On the other
hand, according to the exemplary embodiment of (b) of FIG. 13, as a
result of the channel monitoring on the secondary channel, if the
secondary channel is in the busy state during the PIFS time period,
the communication node may not transmit a frame through the
secondary channel, and may perform fallback transmission of the
frame only through the primary channel.
[0147] FIG. 14 is a conceptual diagram illustrating a second
exemplary embodiment of a frame transmission operation through a 20
MHz channel as a result of channel monitoring and random backoff
operation on a primary channel and a secondary channel.
[0148] As shown in FIG. 14, the communication node may transmit a
frame through two channels (e.g., channel 174 and channel 176).
Hereinafter, the channel 174 may be referred to as a first channel,
and the channel 176 may be referred to as a second channel.
[0149] The communication node may perform monitoring on the
channels (e.g., the first channel and/or the second channel) before
transmitting a non-real-time frame (e.g., frame including a best
effort and/or background payload, etc.). According to the exemplary
embodiment of FIG. 14, when one channel among the channels is
occupied by another communication node, the communication node may
wait until the busy state of the occupied one channel ends.
[0150] When the one occupied channel transitions from the busy
state to the idle state, the communication node may identify
whether the channels (e.g., the first channel and the second
channel) are busy by monitoring the channels during a preset AIFS
time period.
[0151] As a result of the channel monitoring, if the channels
(e.g., primary channel and secondary channel) are not busy during
the preset AIFS time period, the communication node may perform
random backoff operations on the channels. The communication node
may independently perform the random backoff operation on each of
the channels. That is, the communication node may perform the
random backoff operation on the primary channel during a first
period, and may perform the random backoff operation on the
secondary channel during a second period. The first period may be a
period having a length different from that of the second period.
Specifically, the first period may be AC_BE of FIG. 4, and the
second period may be AC_BK of FIG. 4. The communication node may
determine a primary channel among the channels by comparing the
lengths of the first period and the second period. As in the
exemplary embodiment of FIG. 14, when the first period is longer
than the second period, the communication node may configure the
second channel as a primary channel and configure the first channel
as a secondary channel.
[0152] The communication node may perform a random backoff
operation for channel access on the primary channel (e.g., the
second channel) and may perform a random backoff operation on the
secondary channel (e.g., the first channel). In addition, the
communication node may perform a channel monitoring operation on
the secondary channel during a preset time period. The length of
the preset time period may be a PIFS, and the ending time of the
PIFS may be the same as the time of completing the random backoff
operation on the secondary channel (e.g., the first channel).
[0153] The communication node may detect a busy state of the
primary channel (e.g., the second channel). As a result of the
channel monitoring on the secondary channel, if the secondary
channel is idle during the PIFS time period, the communication node
may change the configuration of the primary channel and the
secondary channel. Specifically, when the first period is shorter
than a sum of the lengths of the second period, the busy period of
the second channel, and the AIFS time period, the communication
node may change the configuration by configuring the first channel
as a primary channel. The communication node may change the
configuration by configuring the second channel as a secondary
channel, and may perform a channel monitoring operation on the
changed secondary channel during a preset time period. The length
of the preset time period may be a PIFS, and the ending time of the
PIFS may be the same as the time of completing the random backoff
operation on the changed primary channel.
[0154] If the random backoff operation is completed on the changed
primary channel (e.g., the first channel), and the changed
secondary channel (e.g., the second channel) is in the idle state
during the PIFS time period as a result of the channel monitoring
on the changed secondary channel, the communication node may
transmit a frame through the primary channel and the secondary
channel.
[0155] In FIGS. 7 to 14, the communication node may perform the
same operation not only for the 10 MHz channel but also for the 20
MHz channel. The communication node intending to transmit a 20 MHz
PPDU may perform random backoff operations on a plurality of
channels by using a plurality of backoff counters, and then
transmit a frame through channels on which the random backoff
operations are completed. The transmission starting times and the
transmission ending times of frames transmitted through all
channels may be the same, respectively. When the transmission
ending times of the respective frames are different, the
communication node may add padding to shorter frames to match the
ending times of the frames. Here, the term `channel` may be
replaced by a term `link`. The primary channel may be referred to
as `one link` or `primary link`, the secondary channel may be
referred to as `another link` or `secondary link`, and a link may
include a channel. A 10 MHz PPDU may mean a frame transmitted using
only one link.
[0156] FIG. 15 is a conceptual diagram illustrating an exemplary
embodiment of a structure of a multi-link established between an AP
and a STA of a communication node.
[0157] As shown in FIG. 15, a communication node may perform frame
transmission/reception operations using a multi-link by applying a
non-contiguous bandwidth extension technique (e.g., 80 MHz+80 MHz
transmission). The communication node using a multi-link may
perform multi-band transmission. For example, the communication
node may perform frame transmission by using a 40 MHz bandwidth
through the conventional channel extension scheme in the 2.4 GHz
band, and a 160 MHz bandwidth through the conventional channel
extension scheme in the 5 GHz band. Alternatively, the
communication node may perform communication by using a 160 MHz
bandwidth in the 6 GHz band while performing communication using a
160 MHz bandwidth in the 5 GHz band. One frequency band used by the
communication node may be defined as one link. Alternatively, the
communication node may establish a plurality of links in one
frequency band. For example, the communication node may establish
one link in the 2.4 GHz band and two links in the 6 GHz band.
[0158] The AP and the communication node (e.g., STA) supporting the
multi-link operation may perform an access operation and a
negotiation operation for the multi-link operation to configure the
number of links and links to be used. The communication node may
identify information on band(s) capable of performing communication
with the wireless AP. The communication node may configure a part
or all of the links supported by the wireless AP to be used for the
multi-link operation in a negotiation procedure through the
multi-link operation with the wireless AP. A communication node
that does not perform the multi-link operation (e.g., IEEE
802.11a/b/g/n/ac/ax communication node) may be connected to some
links supported by the AP.
[0159] Some of the links available in the wireless AP may have
sufficient band separations, so that one communication node can
perform simultaneous transmission and reception operations by using
the links. On the other hand, if some of the links available in the
wireless AP do not have sufficient band separations, simultaneous
transmission and reception operations using the links may not be
possible due to a phenomenon (e.g., in-device coexistence (IDC)
interference) in which transmission on one link causes interference
to another link within the communication node. For example, the
communication node may configure a multi-link including a first
link, a second link, and a third link with the AP. If a band
separation between the first link and the third link is sufficient,
the communication node may receive a frame through the third link
at the same time while transmitting a frame through the first link.
On the other hand, if the band separation between the first link
and the third link is insufficient, the communication node
transmitting a frame through the first link may not receive a frame
through the second link.
[0160] FIG. 16 is a conceptual diagram illustrating a first
exemplary embodiment of a frame transmission operation through at
least one link among a plurality of links as a result of random
backoff operations on the plurality of links.
[0161] As shown in FIG. 16, a communication node may transmit
frames through a plurality of links (e.g., a first link and a
second link). The communication node of FIG. 16 may be a multi-link
device (MLD) supporting multi-link communication. In addition, the
communication node of FIG. 16 may be a non-simultaneous transmit
and receive (non-STR) MLD that cannot simultaneously perform a
frame transmission operation and a frame reception operation. The
MLD may use a different MAC address for each link, so that it can
operate as if a different communication node exists for each link
although it is a single communication device. For example, an
operation of a first MLD having the first link and the second link
may be regarded as that a first STA operates on the first link and
a second STA operates on the second link.
[0162] The communication node may perform random backoff operations
on the links. The communication node may independently perform the
random backoff operation on each of the links. That is, the
communication node may perform the random backoff operation on the
first link during a first period, and may perform the random
backoff operation on the second link during a second period. The
first period may be a period having a length different from that of
the second period. In order to determine the first period and the
second period, the communication node may select random backoff
counter values according to a rule set for each AC according to a
type of a frame to be transmitted when performing the random
backoff. The communication node may randomly select two random
backoff counters to be applied to the first period and the second
period at the same time.
[0163] The communication node (e.g., first STA) may complete the
random backoff operation on the first link among the links. In
addition, the communication node (e.g., the second STA) may detect
a busy state of the second link during the random backoff operation
on the second link. The first STA of the communication node may
access the first link and may transmit a first PPDU through the
first link. On the other hand, when the first STA of the
communication node transmits the first PPDU through the first link,
the second STA of the communication node may not be able to perform
a frame reception operation through the second link even after the
busy state of the second link ends. Specifically, while the first
STA of the communication node transmits the first PPDU, the second
STA of the communication node may not perform a link sensing
operation on the second link because the second STA of the
communication node cannot perform a reception operation on the
second link. A period in which the second STA of the communication
node cannot perform the link sensing operation on the second link
may be referred to as a `deaf period`. During the deaf period, the
second STA of the communication node may freeze the random backoff
operation on the second link.
[0164] When the first STA of the communication node has completed
transmitting the first PPDU on the first link, the deaf period of
the second STA of the communication node may end. The second STA of
the communication node may resume the random backoff operation on
the second link. When the random backoff operation on the second
link is completed as a result of the resumption of the random
backoff operation of the second STA of the communication node, the
second STA of the communication node may transmit a second PPDU on
the second link.
[0165] FIG. 17 is a conceptual diagram illustrating a second
exemplary embodiment of a frame transmission operation through at
least one link among a plurality of links as a result of random
backoff operations on the plurality of links.
[0166] As shown in FIG. 17, a communication node may transmit
frames through a plurality of links (e.g., a first link and a
second link). The communication node of FIG. 17 may be a non-STR
MLD that cannot simultaneously perform a frame transmission
operation and a frame reception operation. The MLD may use a
different MAC address for each link, so that it can operate as if a
different communication node exists for each link although it is a
single communication device. For example, an operation of a first
MLD having the first link and the second link may be regarded as
that a first STA operates on the first link and a second STA
operates on the second link.
[0167] The communication node may perform random backoff operations
on the links. The communication node may independently perform the
random backoff operation on each of the links. That is, the
communication node may perform the random backoff operation on the
first link during a first period, and may perform the random
backoff operation on the second link during a second period. The
first period may be a period having a length different from that of
the second period. In order to determine the first period and the
second period, the communication node may select random backoff
counter values according to a rule set for each AC according to a
type of a frame to be transmitted when performing the random
backoff. The communication node may randomly select two random
backoff counters to be applied to the first period and the second
period at the same time.
[0168] The communication node (e.g., the first STA) may complete
the random backoff operation on one link (e.g., the first link)
among the links. The first STA of the communication node may
identify a remaining random backoff counter value of the second STA
of the communication node at the time of completing the random
backoff operation on the first link. The first STA of the
communication node may determine whether to transmit a first PPDU
based on a result of comparison between the remaining random
backoff counter value of the second STA of the communication node
and a preset threshold. The preset threshold may be proportional to
a transmission time of the PPDU. Alternatively, the preset
threshold may be proportional to a delay limit value of the PPDU.
The first STA of the communication node may adjust the preset
threshold by reflecting a normalization factor. The normalization
factor may be a number greater than 0 and less than or equal to
1.
[0169] When the remaining random backoff counter value of the
second STA of the communication node is less than the preset
threshold, the first STA of the communication node may wait before
transmitting the first PPDU through the first link. The second STA
of the communication node may perform the random backoff operation
on the second link. In addition, the first STA of the communication
node may perform a link monitoring operation on the first link
during a preset time period. The length of the preset time period
may be a PIFS, and the ending time of the PIFS may be the same as
the time of completing the random backoff operation on the second
link of the second STA of the communication node. For example, the
first STA of the communication node may perform an energy detection
(ED) operation to detect a frame from another communication
node.
[0170] As a result of the link monitoring operation of the first
STA of the communication node, if the first link is in the idle
state during the PIFS time period and the second STA completes the
random backoff operation on the second link, the communication node
may transmit frames through the first link and the second link.
[0171] As a result of the link monitoring operation of the first
STA of the communication node, if the first link is busy during the
PIFS time period, the communication node (e.g., the second STA) may
transmit the first PPDU and a second PPDU through the second link.
In addition, when the second STA of the communication node detects
a busy state of the second link during the random backoff
operation, the communication node (e.g., the first STA) may
transmit the first PPDU and the second PPDU. When the first PPDU
and the second PPDU exceed a maximum transmission period (MAX
TXOP), the communication node may transmit the first PPDU and the
second PPDU by using a fragmentation scheme.
[0172] FIG. 18 is a conceptual diagram illustrating a third
exemplary embodiment of a frame transmission operation through at
least one link among a plurality of links as a result of random
backoff operations on the plurality of links.
[0173] As shown in FIG. 18, a communication node may transmit
frames through a plurality of links (e.g., a first link and a
second link). The communication node of FIG. 18 may be a non-STR
MLD that cannot simultaneously perform a frame transmission
operation and a frame reception operation. The MLD may use a
different MAC address for each link, so that it can operate as if a
different communication node exists for each link although it is a
single communication device. For example, an operation of a first
MLD having the first link and the second link may be regarded as
that a first STA operates on the first link and a second STA
operates on the second link.
[0174] The communication node may perform random backoff operations
on the links. The communication node may independently perform the
random backoff operation on each of the links. That is, the
communication node may perform the random backoff operation on the
first link during a first period, and may perform the random
backoff operation on the second link during a second period. The
first period may be a period having a length different from that of
the second period. In order to determine the first period and the
second period, the communication node may select random backoff
counter values according to a rule set for each AC according to a
type of a frame to be transmitted when performing the random
backoff. The communication node may randomly select two random
backoff counters to be applied to the first period and the second
period at the same time.
[0175] The communication node (e.g., the first STA) may complete
the random backoff operation on one link (e.g., the first link)
among the links. The first STA of the communication node may
identify a remaining random backoff counter value of the second STA
of the communication node at the time of completing the random
backoff operation on the first link. The first STA of the
communication node may determine whether to transmit a first PPDU
based on a result of comparison between the remaining random
backoff counter value of the second STA of the communication node
and a preset threshold. The preset threshold may be proportional to
a transmission time of a frame or a delay limit value of a frame.
The first STA of the communication node may adjust the preset
threshold by reflecting a normalization factor.
[0176] When the remaining random backoff counter value of the
second STA of the communication node is greater than the preset
threshold, the first STA of the communication node may transmit the
first PPDU and a second PPDU through the first link. When the first
PPDU and the second PPDU exceed a maximum transmission period (MAX
TXOP), the communication node may transmit the first PPDU and the
second PPDU by using a fragmentation scheme.
[0177] FIG. 19 is a conceptual diagram illustrating a fourth
exemplary embodiment of a frame transmission operation through at
least one link among a plurality of links as a result of random
backoff operations on the plurality of links.
[0178] As shown in FIG. 19, a first communication node may transmit
frames through a plurality of links (e.g., a first link and a
second link). The first communication node of FIG. 19 may be a
non-STR MLD that cannot simultaneously perform a frame transmission
operation and a frame reception operation. The MLD may use a
different MAC address for each link, so that it can operate as if a
different first communication node exists for each link although it
is a single communication device. For example, an operation of a
first MLD having the first link and the second link may be regarded
as that a first STA operates on the first link and a second STA
operates on the second link.
[0179] The first communication node may perform random backoff
operations on the links. The first communication node may
independently perform the random backoff operation on each of the
links. That is, the communication node may perform the random
backoff operation on the first link during a first period, and may
perform the random backoff operation on the second link during a
second period. The first period may be a period having a length
different from that of the second period. In order to determine the
first period and the second period, the first communication node
may select random backoff counter values according to a rule set
for each AC according to a type of a frame to be transmitted when
performing the random backoff. The first communication node may
randomly select two random backoff counters to be applied to the
first period and the second period at the same time.
[0180] The first communication node (e.g., the first STA) may
complete the random backoff operation on one link (e.g., the first
link) among the links. The first STA of the first communication
node having completed the random backoff operation may acquire a
transmission opportunity (TXOP). However, the first STA of the
first communication node may delay transmission of a frame (e.g.,
first PPDU) until the random backoff of the second STA of the first
communication node is completed. The first STA having completed the
random backoff operation on the first link may transmit a sharing
frame to a second communication node including an AP through the
first link. A value of a duration field in a MAC header of the
sharing frame may be set to (length t0 of the TXOP-transmission
length of the sharing frame) according to the 802.11 specification.
Alternatively, the value of the duration field of the MAC header
according to an exemplary embodiment of the present disclosure may
be set to (t2-length of the sharing frame). The sharing frame may
have a structure described below.
[0181] FIG. 20 is a conceptual diagram illustrating an exemplary
embodiment of a structure of a sharing frame transmitted by a first
communication node.
[0182] As shown in FIG. 20, the sharing frame transmitted by the
first communication node may include a basic MAC header part, a
multi-link information field indicating multi-link information, a
backoff information field indicating information on a random
backoff operation, and an error detection part (i.e., frame check
sequence (FCS)) used to detect whether there is an error in the
transmitted sharing frame. The MAC header part may include a frame
control field for configuring a frame type and the like, and a
duration/ID field for configuring a TXOP. In addition, the MAC
header of the sharing frame may further include a receiver address
(RA) field and a transmitter address (TA) field of the sharing
frame.
[0183] The sharing frame may further include the multi-link
information field indicating multi-link information, the backoff
information field indicating information on a random backoff
operation, and an FCS for detecting an error in the sharing
frame.
[0184] The multi-link information field may indicate whether
simultaneous transmit/receive (STR) is supported (i.e., STR
capability), link assignment information (i.e., assigned link
bitmap), a length of a Sub-TXOP, and the like. The STR capability
field may indicate whether the first communication node supports
simultaneous frame transmission/reception. When the first
communication node supports simultaneous frame
transmission/reception, a bit of the STR capability field may be
set to 0, and the sharing frame may not include the backoff
information field. The link assignment information field may
indicate links currently used for frame transmission among links
assigned to the first communication node. When the first
communication node configures a multi-link with the AP, the link
assignment field may indicate links currently used in transmission
among all the links assigned to the first communication node. Bits
of the link assignment information field may be mapped in the order
of assigned link numbers. A bitmap of the link assignment
information field may have a size of 8 bits and may indicate up to
8 links currently being used for data transmission among eight
assigned links. For example, if the bitmap of the link assignment
information field is set to `1100000`, the first link and the
second link are currently used for transmission, and the backoff
information field may include backoff information of the two links.
The length of the Sub-TXOP may indicate a period available for
transmission without a separate channel access procedure from a
time after an SIFS time period elapses from the time of completing
the transmission of the sharing frame to the time of completing the
random backoff operation on the second link. The Sub-TXOP may use
the same time unit as the duration field of the MAC header.
[0185] The link backoff information field may include information
on a remaining backoff counter value to be used in another link.
When starting channel access to multi-links, the first
communication node may randomly select as many backoff counters as
the number of links, and may start random backoff operations with
one backoff counter value among the selected backoff counters. The
first communication node may use the smallest backoff counter value
among the selected backoff counter values for a link through which
the sharing frame is to be transmitted. The link backoff
information field may include information on remaining random
backoff counter values of other links at the time of transmitting
the sharing frame. Upon receiving the remaining random backoff
counter value, the AP may set and use a time value obtained by
subtracting a time consumed for transmission of the sharing frame
from the received remaining backoff counter value as a remaining
backoff counter value to be actually used.
[0186] Referring back to FIG. 19, the second communication node
including the AP may receive the sharing frame through the first
link of the first communication node (e.g., the first MLD). The
second communication node including the AP may calculate a
transmission period (i.e., Sub-TXOP) of the second communication
node based on the parameters of the received sharing frame. The
transmission period (i.e., Sub-TXOP) of the second communication
node may be calculated through an equation <t1-t2-2*(SIFS or
PIFS)>. The second communication node may transmit ACK for the
sharing frame to the first communication node (e.g., the first STA)
after a preset period (e.g., SIFS) elapses from the time of
receiving the sharing frame. The ACK may have a structure described
below.
[0187] FIG. 21 is a conceptual diagram illustrating an exemplary
embodiment of a structure of an ACK frame for a sharing frame.
[0188] As shown in FIG. 21, the ACK frame for the sharing frame may
include a MAC header part, a link status information part including
link status information, and an error detection part used to detect
whether the transmitted ACK frame has an error. The MAC header part
may include a frame control field for configuring a frame type, a
duration/ID field for configuring a TXOP, a receiver address field,
and the like.
[0189] The ACK frame may further include a multi-link status
information field indicating statuses of the multi-link, a busy
information field indicating occupancy information, and an error
detection part (i.e., frame check sequence (FCS)) used to detect
whether the transmitted ACK frame has an error.
[0190] The multi-link status information field may further include
a link status bitmap. The multi-link status information field may
indicate a link occupied by another communication node during
transmission of the sharing frame among a plurality of links
currently used for transmission indicated by the bitmap of the link
assignment information field of the sharing frame. For example,
when the multi-link status information field is set to `01000000`,
it may indicate that the second link was occupied by another
communication node during transmission of the sharing frame.
[0191] The busy information field may indicate occupancy
information of each of the links, for which a corresponding bit in
the link status bitmap is set to 1. The busy information field may
be configured based on information on a transmission time of the
frame occupying the link, and may be configured as a remaining
transmission time after the ACK frame is transmitted based on the
duration field value of the MAC header. If the second communication
node including the AP does not allow use of some links among the
multi-links that the first communication node requested to use
through the sharing frame, the second communication node may set a
bit corresponding to a link that is not allowed to use in the
multi-link status information field to 1, and may set a period,
that is not allowed, in the busy information field.
[0192] Referring back to FIG. 19, the second communication node
having transmitted the ACK may wait for a preset time period (e.g.,
SIFS or PIFS) for ED or PD sensing on the first link, and then
transmit a frame through the first link during a Sub-TXOP time
period. During the Sub-TXOP time period, the second communication
node may transmit a frame to an arbitrary STA including the first
STA that is a non-STR MLD. The second communication node may
transmit only a frame having a length within a time period of t3.
If there is no payload to be transmitted to an arbitrary STA, the
second communication node may not transmit a frame during the
Sub-TXOP time period, or transmit a Quality of service (QoS) null
frame in which a duration value of a MAC header is set to the value
of the Sub-TXOP.
[0193] After the Sub-TXOP, the first STA may perform a link
monitoring operation on the first link during a preset time period.
The length of the preset time period may be a PIFS, and the ending
time of the PIFS may be the same as the time of completing the
random backoff operation of the second STA on the second link. For
example, the first STA may detect a frame from another first
communication node by performing an ED or PD sensing operation.
[0194] As a result of the link monitoring operation of the first
STA, if the first link is in the idle state during the PIFS time
period and the second STA completes the random backoff operation on
the second link, the first communication node may simultaneously
transmit the first PPDU and the second PPDU through the first link
and the second link.
[0195] The second communication node including the AP may receive
the first PPDU and the second PPDU through the first link and the
second link, and after a SIFS time period, the second communication
node may simultaneously transmit block ACK (BA) frames respectively
indicating reception statuses of the first and second PPDUs through
the first link and the second link. If a busy state of the second
link is detected while performing the random backoff operation on
the second link, the first communication node (e.g., STA 1) may
transmit the first PPDU and the second PPDU through the first
link.
[0196] FIGS. 22A to 22C are conceptual diagrams illustrating a
fifth exemplary embodiment of a frame transmission operation
through at least one link among a plurality of links as a result of
random backoff operations on the plurality of links.
[0197] As shown in FIGS. 22A to 22C, a first communication node may
transmit frames through a plurality of links (e.g., a first link
and a second link). The first communication node of FIGS. 22A to
22C may be a non-STR MLD that cannot simultaneously perform a frame
transmission operation and a frame reception operation. The MLD may
use a different MAC address for each link, so that it can operate
as if a different first communication node exists for each link
although it is a single communication device. For example, an
operation of a first MLD having the first link and the second link
may be regarded as that a first STA operates on the first link and
a second STA operates on the second link.
[0198] The first communication node may perform random backoff
operations on the links. The first communication node may
independently perform the random backoff operation on each of the
links. That is, the communication node may perform the random
backoff operation on the first link during a first period, and may
perform the random backoff operation on the second link during a
second period. The first period may be a period having a length
different from that of the second period. In order to determine the
first period and the second period, the first communication node
may select random backoff counter values according to a rule set
for each AC according to a type of a frame to be transmitted when
performing the random backoff. The first communication node may
randomly select two random backoff counters to be applied to the
first period and the second period at the same time.
[0199] The first communication node (e.g., the first STA) may
complete the random backoff operation on one link (e.g., the first
link) among the links. The first STA having completed the random
backoff operation on the first link may transmit a sharing frame to
the second communication node including the AP through the first
link. Specifically, when the random backoff counter value of the
second link is greater than (transmission time of the sharing
frame+SIFS+ACK frame transmission time+.alpha.), the first
communication node may transmit the sharing frame to the second
communication node including the AP. On the other hand, when the
random backoff counter value of the second link is less than
(transmission time of the sharing frame+SIFS+ACK frame transmission
time+.alpha.), the first communication node may transmit frames
through the first and second links after completing the random
backoff operation on the second link.
[0200] The value of the duration field of the MAC header according
to an exemplary embodiment of the present disclosure may be set to
a sum of (the maximum value among random backoff counter values
randomly selected to be applied to a plurality of links currently
used by the MLD for frame transmission+PPDU transmission time+BA
transmission time). .alpha. may be a time corresponding to
(Sub-TXOP+2*(SIFS or PIFS)), and the non-STR MLD may transmit the
sharing frame including the duration value of the MAC header, and
receive ACK. The first communication node may configure a period
corresponding to the duration value as a TXOP, which is a time
available for transmission. A time waiting for the longest backoff
counter of the plurality of links within the configured TXOP may be
given so that another communication node can use the time for
transmission, and such the time is denoted as a `Sub-TXOP` in the
present disclosure. .alpha. may be 0, and this case may correspond
to a case where a PPDU is transmitted immediately after a SIFS time
after receiving the ACK, and it has only an effect of configuring
the TXOP of the first link. The receiver Address (RA) of the
sharing frame may indicate the second communication node including
the AP, which allows to use the Sub-TXOP. The transmitter address
(TA) of the sharing frame may indicate the first STA that has a MAC
address of the first link of the non-STR MLD. In order to allow all
terminals to receive and decode frames during the Sub-TXOP, the
frames may be transmitted by setting the receiver address to a
broadcast address.
[0201] The first communication node that is a non-STR MLD may not
be able to perform simultaneous frame transmission/reception
operations. Accordingly, since the first communication node may not
be able to perform a sensing operation for detecting a state of the
second link by detecting a reception signal in the second link
during the sharing frame transmission through the first link and a
preset time period (e.g., SIFS, etc.) (i.e., during the deaf
period) for transitioning to a receive mode, the first
communication node may not be able to perform a random backoff
operation during the deaf period.
[0202] The second communication node having received the sharing
frame may be a device capable of supporting simultaneous
transmission/reception of frames, and thus the second communication
node may be able to sense all links in which the second
communication node does not transmit frames. Therefore, the second
communication node having received the sharing frame may sense the
link(s) in which simultaneous transmission(s) indicated by the
sharing frame of the first communication node are performed during
the deaf period of the first communication node. The second
communication node including the AP may identify whether the link
(e.g., the second link) is idle as a result of the sensing on the
link(s) during the deaf period, and may notify whether the link(s)
(e.g., second link) are idle to the first communication node
through the link status bitmap and the busy information field of
the ACK frame. If the second link is in the idle state during the
deaf period, the second communication node including the AP may
notify the idle state by setting a bit corresponding to the link in
the link status bitmap of the ACK frame to 0. On the other hand, if
the second link is in the busy state during the deaf period, the
second communication node including the AP may notify information
on the length of the busy period of the second link together.
[0203] As shown in FIG. 22A, when the second link is in the idle
state during the deaf period, the second communication node
including the AP, which is capable of supporting simultaneous
transmission/reception, may notify that the corresponding link is
in the idle state through the ACK frame. The first communication
node may receive the link status from the second communication node
through the ACK frame, and the second STA of the first
communication node may perform a random backoff operation on the
second link. On the other hand, the second communication node
including the AP may transmit frames to the first STA or the first
communication node including the first STA during the Sub-TXOP time
after a preset time period (e.g., PIFS or SIFS) after transmitting
the ACK frame. The second communication node including the AP may
identify the length of the Sub-TXOP to be used for frame
transmission based on the information (e.g., sub-TXOP length field)
received through the sharing frame. After the Sub-TXOP, the first
STA of the non-STR MLD may identify whether the first link is idle
by performing sensing, i.e., a link monitoring operation, on the
first link during a preset time period (e.g., PIFS or SIFS) before
the time of completing the random backoff operation on the second
link.
[0204] As a result of the link monitoring operation of the first
STA of the non-STR MLD, if the first link is in the idle state
during the PIFS or SIFS time period, and the second STA of the
non-STR MLD completes the random backoff operation on the second
link, the first communication node may simultaneously transmit the
first PPDU and the second PPDU through the first link and the
second link. When the length of the first PPDU and the length of
the second PPDU are not equal to each other, the first
communication node may add padding to a shorter frame to match the
ending times of the frames.
[0205] The second communication node including the AP may receive
the first PPDU and the second PPDU through the first link and the
second link, and after a SIFS time period elapses, the second
communication node may receive block ACK request (BAR) frames from
the first communication node simultaneously through the first link
and the second link. After a SIFS time period elapses after
receiving the BAR frame, the first communication node may
simultaneously transmit BAs respectively indicating reception
states of the first PPDU and the second PPDU through the first link
and the second link.
[0206] As shown in FIG. 22B, if the second link is occupied by
another first communication node during the deaf period, the second
communication node including the AP may notify through an ACK frame
that the corresponding link is in the busy state. The first
communication node may identify the busy state by seeing that the
bit of the corresponding link in the link status bitmap of the ACK
frame from the second communication node is set to 1, identify how
long the corresponding link is occupied through the busy
information field received together, and the second STA of the
first communication node that is a non-STR MLD may stop the random
backoff operation on the second link. The first STA of the first
communication node that is a non-STR MLD may perform a link
monitoring operation on the first link during a preset time period
(e.g., PIFS or SIFS) from the time of receiving the ACK frame.
[0207] As a result of the link monitoring operation of the first
STA of the first communication node that is a non-STR MLD, if the
first link is in the idle state during the PIFS or SIFS time
period, the first communication node may transmit a PPDU through
the first link. The transmitted PPDU may be a frame including both
the first PPDU to be transmitted through the first link and the
second PPDU to be transmitted through the second link.
[0208] The second communication node including the AP may receive
the first PPDU and the second PPDU through the first link, and may
transmit a BA indicating the reception states for the first PPDU
and the second PPDU through the first link after the SIFS or PIFS
time period.
[0209] As shown in FIG. 22C, if the second link is in the idle
state during the deaf period, the second communication node
including the AP may transmit an ACK frame. The first communication
node may receive the ACK indicating that the second link is idle
from the second communication node including the AP, and the second
STA of the first communication node that is a non-STR MLD may
perform a random backoff operation on the second link after a SIFS
time elapses after receiving the ACK. A random backoff counter used
for the random backoff operation may use a counter value obtained
by subtracting the deaf period from the initially selected counter
value. The second STA of the first communication node that is a
non-STR MLD may detect the busy state of the second link during the
random backoff operation on the second link. In the case of being
occupied by another communication node while performing the backoff
procedure, the backoff counter may be frozen. The frozen backoff
counter may be used when resuming the channel access. That is, when
the first communication node resumes the channel access and
performs the channel access on the two links, the first
communication node may randomly select only one backoff counter,
and may use the previously frozen backoff counter as the other one.
On the other hand, the second communication node including the AP
may transmit a frame to the first STA or the first communication
node including the first STA through the first link during a
Sub-TXOP after a preset time period (e.g., PIFS or SIFS) elapses
after transmitting the ACK. After the Sub-TXOP, the first STA may
perform a link monitoring operation on the first link during a
preset time period (e.g., PIFS or SIFS) before the time of
completing the random backoff operation on the second link.
[0210] As a result of the link monitoring operation of the first
STA, if the first link is in the idle state during the PIFS or SIFS
time period, the first communication node may transmit the first
PPDU through the first link.
[0211] The second communication node including the AP may receive
the first PPDU through the first link, and may transmit a BA
indicating a reception state of the first PPDU through the first
link after the SIFS time period.
[0212] FIG. 23 is a conceptual diagram illustrating a sixth
exemplary embodiment of a frame transmission operation through at
least one link among a plurality of links as a result of random
backoff operations on the plurality of links.
[0213] As shown in FIG. 23, a first communication node may transmit
frames through a plurality of links (e.g., a first link and a
second link). The first communication node of FIG. 23 may be a
non-STR MLD that cannot simultaneously perform a frame transmission
operation and a frame reception operation. The MLD may use a
different MAC address for each link, so that it can operate as if a
different first communication node exists for each link although it
is a single communication device. For example, an operation of a
first MLD having the first link and the second link may be regarded
as that a first STA operates on the first link and a second STA
operates on the second link.
[0214] The first communication node may perform random backoff
operations on the links. The first communication node may
independently perform the random backoff operation on each of the
links. That is, the communication node may perform the random
backoff operation on the first link during a first period, and may
perform the random backoff operation on the second link during a
second period. The first period may be a period having a length
different from that of the second period. In order to determine the
first period and the second period, the first communication node
may select random backoff counter values according to a rule set
for each AC according to a type of a frame to be transmitted when
performing the random backoff. The first communication node may
randomly select two random backoff counters to be applied to the
first period and the second period at the same time.
[0215] The first communication node (e.g., the first STA) may
complete the random backoff operation on one link (e.g., the first
link) among the links. The first STA having completed the random
backoff operation on the first link may transmit a sharing frame to
the second communication node including the AP through the first
link. The value of the duration field of the MAC header may be set
to (t2-transmission time of the sharing frame+SIFS+ACK frame
transmission time).
[0216] The first communication node having completed the random
backoff operation on one link (e.g., the first link) may stop the
random backoff operation on the other link (e.g., the second link)
by resetting the random backoff counter in the other link.
[0217] The second communication node including the AP may receive
the sharing frame from the first communication node (e.g., the
first STA). The second communication node including the AP may
calculate a transmission period (i.e., Sub-TXOP) of the second
communication node based on the parameters of the received sharing
frame. The second communication node transmit an ACK frame for the
sharing frame to the first communication node (e.g., the first STA)
after a preset period (e.g., SIFS) elapses from the time of
receiving the sharing frame. After transmitting the ACK frame, the
second communication node including the AP may wait for a preset
time period (e.g., SIFS or PIFS) in the first link, and then
transmit frames to the first communication node including a non-STR
MLD through the first link during the Sub-TXOP time period. When
the lengths of frames to be transmitted to the first communication
nodes are different from each other, the second communication node
may add padding to shorter frames according to the ending time of
the Sub-TXOP time period to match the ending times of the frames.
If there is no payload to be transmitted during the Sub-TXOP time
period, the second communication node including the AP may not
transmit frames during the Sub-TXOP time period, or may transmit a
QoS null frame in which a duration value of a MAC header is set to
the Sub-TXOP value.
[0218] In addition, the second communication node including the AP
may perform a random backoff operation on the second link from the
time of receiving the sharing frame. Specifically, the second
communication node including the AP may continuously perform the
random backoff operation on the second link, that was performed by
the first communication node, based on a remaining random backoff
counter value of the second link included in the sharing frame.
That is, the total random backoff counter performed for the second
link may be the random backoff value initially selected by the
first communication node. The second communication node including
the AP may perform the random backoff operation from the time of
receiving the sharing frame, and the random backoff counter value
may be set to a value obtained by subtracting the transmission time
of the sharing frame from the remaining backoff counter value t1.
Accordingly, the second communication node including the AP may
perform the random backoff operation during the same time period as
the remaining time period of the random backoff operation of the
first communication node (e.g., the second STA of the MLD).
[0219] After the Sub-TXOP, if the first link is in the idle state
during a preset time period (e.g., SIFS or PIFS) from the ending
time of the Sub-TXOP, and the second communication node including
the AP completes the random backoff operation on the second link,
the second communication node may transmit a trigger frame (TF) to
the first communication node through the first link and the second
link. If the second communication node including the AP fails to
complete the random backoff operation by detecting the busy state
of the second link during the random backoff operation on the
second link, the second communication node may transmit a trigger
frame through the first link. The RA of the trigger frame may be
set in form of a MAC address. Specifically, the RA of the trigger
frame transmitted through the first link may be set to a MAC
address of the first STA of the first communication node that is a
non-STR MLD, and the RA of the trigger frame transmitted through
the second link may be set to a MAC address of the second STA of
the first communication node that is a non-STR MLD. The trigger
frames may include information on the lengths of transmission
frames (or PPDUs) of the first STA and the second STA,
respectively.
[0220] The first communication node may receive the trigger frames
through the first link and the second link. The first STA of the
first communication node may transmit a first PPDU through the
first link. The second STA of the first communication node may
transmit a second PPDU through the second link. The length of the
first PPDU and the length of the second PPDU transmitted through
the respective links may be indicated by the trigger frames
received through the respective links. When the length of the first
PPDU and the length of the second PPDU are not equal to each other,
the first communication node may add padding to a shorter frame to
match the ending times of the frames.
[0221] The first communication node receiving the trigger frames
through the first link and the second link may simultaneously
transmit the first PPDU and the second PPDU through the first link
and the second link.
[0222] The second communication node including the AP may receive
the first PPDU and the second PPDU through the first link and the
second link, and after a SIFS time period elapses, the second
communication node may simultaneously transmit BAs respectively
indicating reception states of the first and second PPDUs through
the first link and the second link. The BA may indicate the
reception states of all frames included in the first PPDU and the
second PPDU. The first communication node may duplicate the BA and
transmit the duplicated BAs simultaneously through the first link
and the second link.
[0223] FIGS. 24A to 24C are conceptual diagrams illustrating a
seventh exemplary embodiment of a frame transmission operation
through at least one link among a plurality of links as a result of
random backoff operations on the plurality of links.
[0224] As shown in FIGS. 24A to 24C, a first communication node may
transmit frames through a plurality of links (e.g., a first link
and a second link). The first communication node of FIGS. 24A to
24C may be a non-STR MLD that cannot simultaneously perform a frame
transmission operation and a frame reception operation. The MLD may
use a different MAC address for each link, so that it can operate
as if a different first communication node exists for each link
although it is a single communication device. For example, an
operation of a first MLD having the first link and the second link
may be regarded as that a first STA operates on the first link and
a second STA operates on the second link.
[0225] The first communication node may perform random backoff
operations on the links. The first communication node may
independently perform the random backoff operation on each of the
links. That is, the communication node may perform the random
backoff operation on the first link during a first period, and may
perform the random backoff operation on the second link during a
second period. The first period may be a period having a length
different from that of the second period. In order to determine the
first period and the second period, the first communication node
may select random backoff counter values according to a rule set
for each AC according to a type of a frame to be transmitted when
performing the random backoff. The first communication node may
randomly select two random backoff counters to be applied to the
first period and the second period at the same time.
[0226] The first communication node (e.g., the first STA) may
complete the random backoff operation on one link (e.g., the first
link) among the links. The first STA having completed the random
backoff operation on the first link may transmit a sharing frame to
the second communication node including the AP through the first
link. The value of the duration field of the MAC header of the
sharing frame may be transmitted as being set to t0 that is a TXOP
value used for the entire transmission. The second communication
node receiving the sharing frame may configure a TXOP used for the
entire transmission based on the sharing frame.
[0227] The first communication node may be a non-STR MLD that
cannot perform simultaneous frame transmission/reception
operations. Therefore, the first communication node may not be able
to perform the random backoff operation on the second link during
the sharing frame transmission through the first link and a preset
time period (e.g., SIFS) (i.e., during the deaf period) required
for transitioning to a receive mode. The first communication node
having completed the random backoff operation on one link (e.g.,
the first link) may deliver a remaining random backoff counter of
the other link to the second communication including the AP through
the sharing frame. The second communication node including the AP
may continuously perform the random backoff operation on the second
link.
[0228] The second communication node including the AP may perform a
random backoff operation on the second link from the time of
receiving the sharing frame. Specifically, the second communication
node may perform the remaining backoff operation on the
corresponding link subsequently to the first communication node
based on the assigned link bitmap and the random backoff counter
value included in the sharing frame. Specifically, in the present
exemplary embodiment, the remaining random backoff operation of the
first communication node may be continuously performed on the
second link. The second communication node including the AP may
perform a different random backoff operation if a frame to be
transmitted occurs and a random backoff should be performed while
performing the random backoff on behalf of the first communication
node. When the random backoff for its own frame is successful, the
second communication node may stop the random backoff operation
performed at the request of the first communication node. The
second communication node having received the sharing frame may
support simultaneous frame transmission/receptions, and thus may
sense all links excluding links through which frames are
transmitted by itself. Accordingly, the second communication node
including the AP receiving the sharing frame may sense the links
with the first communication node during the deaf period of the
first communication node. The second communication node may
identify whether the link (e.g., the second link) is idle as a
result of the link sensing, and transmit information on whether the
link (e.g., second link) is idle to the first communication node
through an ACK frame. If the second link is in the idle state
during the deaf period, the second communication node including the
AP may notify the idle state of the second link by setting a bit
corresponding to the second link in the link status bitmap of the
ACK frame to 0. On the other hand, if the second link is in the
busy state during the deaf period, the second communication node
including the AP may notify the busy state by setting the bit
corresponding to the second link in the link status bitmap of the
ACK frame to 1. When notifying the busy state of the second link,
the second communication node including the AP may notify
information on the length of the busy period of the second link
together.
[0229] As shown in FIG. 24A, if the second link is in the idle
state during the deaf period, the second communication node
including the AP may notify that the second link is in the idle
state through an ACK frame. The first communication node may
receive the ACK frame from the second communication node. After a
preset time period (e.g., PIFS or SIFS) elapses from the time of
transmitting the ACK frame, the second communication node may
transmit a frame(s) to the first communication node(s) during a
Sub-TXOP calculated by referring to Sub-TXOP information included
in the sharing frame. The second communication node performing
transmissions to a plurality of first communication nodes may
perform multi-user transmission by using an orthogonal frequency
division multiple access (OFDMA) scheme. A MAC frame transmitted by
the second communication node including the AP may be a trigger
frame, and an RA of the trigger frame may be a broadcast address.
The second communication node may sense the second link for a
backoff operation performed subsequently from the first
communication node on the second link, and sense the first link
during a preset time period (e.g., PIFS or SIFS) after the
Sub-TXOP. If the second communication node including the AP
completes the random backoff operation on the second link, and the
first link is in the idle state during a PIFS or SIFS, which is the
preset period, the second communication node including the AP may
transmit a trigger frame to the first communication node through
each of the first link and the second link. The RA of the trigger
frame may be set in form of a MAC address. Specifically, the RA of
the trigger frame transmitted through the first link may be set to
a MAC address of the first STA of the first communication node that
is a non-STR MLD, and the RA of the trigger frame transmitted
through the second link may be set to a MAC address of the second
STA of the first communication node that is a non-STR MLD. The
trigger frames may include information on lengths of the
transmission frames (or PPDUs) of the first STA or the second STA,
respectively.
[0230] The first communication node may receive the trigger frames
through the first link and the second link. The first STA of the
first communication node may transmit a first PPDU through the
first link. The second STA of the first communication node may
transmit a second PPDU through the second link.
[0231] The second communication node including the AP may receive
the first PPDU and the second PPDU through the first link and the
second link, and after a SIFS time period, the second communication
node may simultaneously transmit BAs respectively indicating
reception states of the first PPDU and the second PPDU through the
first link and the second link.
[0232] Referring to FIG. 24B, if the second link is in the busy
state during the deaf period, that is, if the second communication
node including the AP occupies the second link before transmitting
the ACK frame, the second communication may notify the busy state
by setting a bit corresponding to the occupied link in the link
status bitmap of the ACK frame to 1. When the second communication
node including the AP notifies the busy state, information on the
length of the busy period may be notified through the busy
information field together with the busy state.
[0233] The first link may be monitored during a preset time period
(e.g., PIFS or SIFS) from the time of transmitting the ACK frame,
and if the first link is in the idle state during the preset time
period, the second communication node including the AP may transmit
a trigger frame to the first communication node through the first
link. The RA of the trigger frame may be set to a MAC address of
the first STA of the first communication node. The trigger frame
may include information on a length of the frame (or PPDU)
transmitted by the first STA of the first communication node.
Similarly, in the case of receiving the trigger frame without being
notified of the busy state through the ACK frame, the first
communication node may determine that the second link is busy, and
thus may transmit the frame only through the first link.
[0234] The first communication node may receive the trigger frame
through the first link. The first STA of the first communication
node may transmit a PPDU including all data to be transmitted
through the first link and the second link.
[0235] The second communication node including the AP may receive
the PPDU through the first link, and may transmit a BA indicating a
reception state of the received PPDU through the first link after a
SIFS time period.
[0236] As shown in FIG. 24C, if the second link is in the idle
state during the deaf period, the second communication node
including the AP may transmit an ACK frame including information
indicating that the second link is in the idle state. The first
communication node may receive the ACK frame from the second
communication node including the AP. The second communication node
including the AP may detect a busy state of the second link during
a random backoff operation on the second link. After a preset time
period (e.g., PIFS or SIFS) elapses from the time of transmitting
the ACK, the second communication node including the AP may
transmit a frame to the first communication node(s) during a
Sub-TXOP period. After the Sub-TXOP, the second communication node
including the AP may monitor the first link during a preset time
period (e.g., PIFS or SIFS), and if the first link is in the idle
state during the preset time period, the second communication node
including the AP may transmit a trigger frame to the first
communication node through the first link. The RA of the trigger
frame may be set to a MAC address of the first STA of the first
communication node. The trigger frame may including information on
a length of a transmission frame (or PPDU) that the first STA of
the first communication node can transmit through the first
link.
[0237] The first communication node may receive the trigger frame
through the first link. The first STA of the first communication
node may transmit a PPDU including data to be included in the first
PPDU and the second PPDU in the first link.
[0238] The second communication node including the AP may receive
the PPDU through the first link, and may transmit a BA indicating a
reception state of the PPDU through the first link after a SIFS
time period.
[0239] FIG. 25 is a conceptual diagram illustrating an eighth
exemplary embodiment of a frame transmission operation through at
least one link among a plurality of links as a result of random
backoff operations on the plurality of links.
[0240] As shown in FIG. 25, a first communication node may transmit
frames through a plurality of links (e.g., a first link and a
second link). The first communication node of FIG. 25 may be a
non-STR MLD that cannot simultaneously perform a frame transmission
operation and a frame reception operation. The MLD may use a
different MAC address for each link, so that it can operate as if a
different first communication node exists for each link although it
is a single communication device. For example, an operation of a
first MLD having the first link and the second link may be regarded
as that a first STA operates on the first link and a second STA
operates on the second link.
[0241] The first communication node may perform random backoff
operations on the links. The first communication node may
independently perform the random backoff operation on each of the
links. The first communication node may detect a busy state of the
second link before completing the random backoff operation on the
first link. The first communication node (e.g., the second STA) may
perform a packet decoding (PD) operation and an ED operation to
obtain information on an ending time of the busy state. The second
STA of the first communication node having obtained the information
on the ending time of the busy state of the second link may set a
NAV, and stop the random backoff operation.
[0242] If the information on the ending time of the busy state of
the second link can be obtained before transmission of a sharing
frame through the first link, t1 informed through the sharing frame
may be set to <remaining NAV counter+AIFS+remaining backoff
counter>.
[0243] The first STA of the first communication node having
completed the random backoff operation on the first link may
transmit the sharing frame to the second communication node
including the AP through the first link. The second communication
node may receive the sharing frame from the first communication
node (e.g., the first STA). The second communication node may
calculate a transmission period (Sub-TXOP) of the second
communication node based on the parameters of the received sharing
frame. The second communication node may transmit an ACK frame for
the sharing frame to the first communication node (e.g., the first
STA) after a preset period (e.g., SIFS) elapses from the time of
receiving the sharing frame.
[0244] The second communication node having transmitted the ACK
frame may wait for a preset time period (e.g., SIFS or PIFS) for ED
or PD sensing on the first link, and then transmit a frame through
the first link during the Sub-TXOP time period.
[0245] After the Sub-TXOP, the first STA of the first communication
node may perform a link monitoring operation on the first link
during a preset time period (e.g., PIFS or SIFS). For example, the
first STA of the first communication node may perform an ED or PD
operation to detect a frame from another first communication
node.
[0246] After the busy state of the second link ends, the second STA
of the first communication node may monitor the second link during
a preset time period (e.g., AIFS). If the second link is in the
idle state during the preset time period (e.g., AIFS), the second
STA of the first communication node may perform a random backoff
operation on the second link.
[0247] As a result of the link monitoring operation of the first
STA of the first communication node, if the first link is in the
idle state during a PIFS time period and the second STA of the
first communication node completes the random backoff operation on
the second link, the first communication node may simultaneously
transmit the first PPDU and the second PPDU through the first link
and the second link.
[0248] The second communication node including the AP may receive
the first PPDU and the second PPDU through the first link and the
second link, and after a SIFS time period, the second communication
node may simultaneously transmit BAs respectively indicating
reception states of the first PPDU and the second PPDU through the
first link and the second link. The BA may indicate reception
states of all frames included in the first PPDU and the second
PPDU. The first communication node may duplicate the BA and
transmit the duplicated BAs simultaneously through the first link
and the second link.
[0249] FIGS. 26A to 26B are conceptual diagrams illustrating a
ninth exemplary embodiment of a frame transmission operation
through at least one link among a plurality of links as a result of
random backoff operations on the plurality of links.
[0250] As shown in FIGS. 26A to 26B, a first communication node may
transmit frames through a plurality of links (e.g., a first link
and a second link). The first communication node of FIGS. 26A to
26B may be a non-STR MLD that cannot simultaneously perform a frame
transmission operation and a frame reception operation. The MLD may
use a different MAC address for each link, so that it can operate
as if a different first communication node exists for each link
although it is a single communication device. For example, an
operation of a first MLD having the first link and the second link
may be regarded as that a first STA operates on the first link and
a second STA operates on the second link.
[0251] The first communication node may perform random backoff
operations on the links. The first communication node may
independently perform the random backoff operation on each of the
links. That is, the communication node may perform the random
backoff operation on the first link during a first period, and may
perform the random backoff operation on the second link during a
second period. The first period may be a period having a length
different from that of the second period. In order to determine the
first period and the second period, the first communication node
may select random backoff counter values according to a rule set
for each AC according to a type of a frame to be transmitted when
performing the random backoff. The first communication node may
randomly select two random backoff counters to be applied to the
first period and the second period at the same time.
[0252] The first communication node (e.g., the first STA) may
complete the random backoff operation on one link (e.g., the first
link) among the links. The first STA of the first communication
node having completed the random backoff operation on the first
link may transmit a sharing frame to the second communication node
including the AP through the first link. The value of the duration
field of the MAC header of the sharing frame may be transmitted as
being set to t0 that is a TXOP value used for the entire
transmission. The second communication node receiving the sharing
frame may configure a TXOP used for the entire transmission based
on the sharing frame. When the first communication node intends to
transmit a PPDU during the Sub-TXOP, the first communication node
may transmit the sharing frame by setting a Sub-TXOP length field
included in the sharing frame to 0.
[0253] The first communication node having completed the random
backoff operation on one link (e.g., the first link) may stop the
random backoff operation on the other link (e.g., the second link)
by resetting the random backoff counter in the other link.
[0254] The second communication node including the AP may receive
the sharing frame from the first communication node (e.g., the
first STA). The second communication node including the AP may
calculate a transmission period (i.e., Sub-TXOP) of the second
communication node based on the Sub-TXOP length field of the
received sharing frame. The second communication node receiving the
sharing frame in which the value of the Sub-TXOP length field is
set to 0 may give a transmission opportunity to the first
communication node, and may not transmit a separate PPDU during the
Sub-TXOP period. The second communication node may transmit an ACK
frame for the sharing frame to the first communication node (e.g.,
the first STA) after a preset period (e.g., SIFS) elapses from the
time of receiving the sharing frame.
[0255] The first communication node having transmitted the sharing
frame by setting the Sub-TXOP length field of the sharing frame to
0 may receive the ACK frame from the second communication node
including the AP. After waiting for a preset time period (e.g.,
SIFS or PIFS) in the first link from the time of receiving the ACK
frame, the first communication node may transmit a first PPDU
through the first link during the Sub-TXOP time period. The first
PPDU may be a PPDU to the second communication node including the
AP. The first communication node may not transmit a frame during
the Sub-TXOP time period, or may transmit a QoS null frame in which
a duration value of a MAC header is set to the Sub-TXOP value.
[0256] In addition, the second communication node including the AP
may perform a random backoff operation on the second link from the
time of receiving the sharing frame. Specifically, the second
communication node may perform a remaining random backoff operation
based on link assignment information and a remaining random backoff
counter value included in the sharing frame. Specifically, in the
present exemplary embodiment, the remaining random backoff
operation of the first communication node may be continuously
performed on the second link. The second communication node
including the AP may perform a different random backoff operation
if a frame to be transmitted occurs and a random backoff should be
performed while performing the random backoff on behalf of the
first communication node. When the random backoff for its own frame
is successful, the second communication node may stop the random
backoff operation performed at the request of the first
communication node. The second communication node including the AP
may perform the random backoff operation from the time of receiving
the sharing frame, and the random backoff counter value used for
the random backoff operation may be set to a value obtained by
subtracting the transmission time of the sharing frame from t1
which is the remaining backoff counter value. Accordingly, the
second communication node including the AP may perform the random
backoff operation during the same time period as the random backoff
operation time period of the first communication node (e.g., the
second STA).
[0257] As shown in FIG. 26A, the first communication node may
transmit the first PPDU during the Sub-TXOP period. After the
Sub-TXOP, if the first link is in the idle state during a preset
time period (e.g., SIFS or PIFS) from the ending time of the
Sub-TXOP, and the second communication node including the AP
completes the random backoff operation on the second link, the
second communication node including the AP may transmit trigger
frames to the first communication node through the first link and
the second link. The RA of the trigger frame may be set in form of
a MAC address. Specifically, the RA of the trigger frame
transmitted through the first link may be set to a MAC address of
the first STA of the first communication node that is a non-STR
MLD, and the RA of the trigger frame transmitted through the second
link may be set to a MAC address of the second STA of the first
communication node that is a non-STR MLD. The trigger frames may
set length information of transmission frames (or PPDUs) of the
first STA and the second STA, respectively.
[0258] The second communication node including the AP may transmit,
to the first communication node, a BA for the frame received
through the first link during the Sub-TXOP time period together
with the trigger frame transmitted through the first link, and
transmit only the trigger frame through the second link. The
transmission length of (BA+trigger frame) of the first link and the
transmission length of the trigger frame of the second link may be
the same. Accordingly, the first communication node may add padding
to the trigger frame of the second link to match the length of the
trigger frame of the second link to the length of the (BA+trigger
frame) of the first link. Alternatively, the second communication
node including the AP may deliver the BA for the first PPDU
transmitted during the Sub-TXOP period later, and in this case,
only the trigger frame may be transmitted also through the first
link.
[0259] The first communication node may receive the trigger frames
(or ACK) through the first link and the second link. The first STA
of the first communication node may transmit the second PPDU
through the first link. The second STA of the first communication
node may transmit the third PPDU through the second link. The
length of the second PPDU and the length of the third PPDU may be
indicated by the trigger frame. When the length of the second PPDU
and the length of the third PPDU are not equal to each other, the
first communication node may add padding to a shorter frame to
match the ending times of the frames.
[0260] The first communication node receiving the trigger frames
through the first link and the second link may simultaneously
transmit the second PPDU and the third PPDU through the first link
and the second link.
[0261] The second communication node including the AP may receive
the second PPDU and the third PPDU through the first link and the
second link, and after a SIFS time period, the second communication
node may simultaneously transmit BAs respectively indicating
reception states of the second and third PPDUs through the first
link and the second link.
[0262] As shown in FIG. 26B, the second communication node
including the AP may detect a busy state of the second link during
the random backoff operation on the second link, and the second
communication node may stop the random backoff operation on the
second link. After the Sub-TXOP, if the first link is in the idle
state during a preset time period (e.g., SIFS or PIFS) from the
ending time of the Sub-TXOP, and the second communication node
stops the random backoff operation on the second link, the second
communication node may transmit a trigger frame to the first
communication node only through the first link. The RA of the
trigger frame may be set to a MAC address of the first STA of the
first communication node. The trigger frame may set length
information of the transmission frame (or PPDU) of the first STA of
the first communication node. Alternatively, the second
communication node may transmit a BA indicating the reception state
of the frame received through the first link during the Sub-TXOP
time period to the first communication node together with the
trigger frame.
[0263] The first communication node may receive the trigger frame
(and BA) through the first link. The first STA of the first
communication node may transmit the second PPDU through the first
link. The length of the second PPDU may be indicated by the trigger
frame. The first communication node receiving the trigger frame
through the first link may transmit the second PPDU through the
first link.
[0264] The second communication node including the AP may receive
the second PPDU through the first link, and may transmit a BA
indicating the reception state of the second PPDU through the first
link after a SIFS time period.
[0265] The exemplary embodiments of the present disclosure may be
implemented as program instructions executable by a variety of
computers and recorded on a computer readable medium. The computer
readable medium may include a program instruction, a data file, a
data structure, or a combination thereof. The program instructions
recorded on the computer readable medium may be designed and
configured specifically for the present disclosure or can be
publicly known and available to those who are skilled in the field
of computer software.
[0266] Examples of the computer readable medium may include a
hardware device such as ROM, RAM, and flash memory, which are
specifically configured to store and execute the program
instructions. Examples of the program instructions include machine
codes made by, for example, a compiler, as well as high-level
language codes executable by a computer, using an interpreter. The
above exemplary hardware device can be configured to operate as at
least one software module in order to perform the embodiments of
the present disclosure, and vice versa.
[0267] While the embodiments of the present disclosure and their
advantages have been described in detail, it should be understood
that various changes, substitutions and alterations may be made
herein without departing from the scope of the present
disclosure.
* * * * *